Document:

EX-4.1

TWENTY-SIXTH SUPPLEMENTAL INDENTURE

dated as of November 19, 2010

This Twenty-Sixth Supplemental Indenture, dated as of the 19th day of November, 2010 between
CMS Energy Corporation, a corporation duly organized and existing under the laws of the State of
Michigan (hereinafter called the “Issuer”) and having its principal office at One Energy Plaza,
Jackson, Michigan 49201, and The Bank of New York Mellon, a New York banking corporation
(hereinafter called the “Trustee”) and having its Corporate Trust Office at 101 Barclay Street, New
York, New York 10286.

WITNESSETH:

WHEREAS, the Issuer and the Trustee (ultimate successor to NBD Bank, National Association)
entered into an Indenture, dated as of September 15, 1992 (the “Original Indenture”), pursuant to
which one or more series of debt securities of the Issuer (the “Securities”) may be issued from
time to time; and

WHEREAS, Section 2.3 of the Original Indenture permits the terms of any series of Securities
to be established in an indenture supplemental to the Original Indenture; and

WHEREAS, Section 8.1(e) of the Original Indenture provides that a supplemental indenture may
be entered into by the Issuer and the Trustee without the consent of any Holders (as defined in the
Original Indenture) of the Securities to establish the form and terms of the Securities of any
series; and

WHEREAS, the Issuer has requested the Trustee to join with it in the execution and delivery of
this Twenty-Sixth Supplemental Indenture in order to supplement and amend the Original Indenture
by, among other things, establishing the form and terms of a series of Securities to be known as
the Issuer’s “5.05% Senior Notes due 2018” (the “2018 Notes”), providing for the issuance of the
2018 Notes and amending and adding certain provisions thereof for the benefit of the Holders of the
2018 Notes; and

WHEREAS, the Issuer and the Trustee desire to enter into this Twenty-Sixth Supplemental
Indenture for the purposes set forth in Section 2.3 and Section 8.1(e) of the Original Indenture as
referred to above; and

WHEREAS, the Issuer has furnished the Trustee with a copy of the resolutions of its Board of
Directors certified by its Secretary or Assistant Secretary authorizing the execution of this
Twenty-Sixth Supplemental Indenture; and

WHEREAS, all things necessary to make this Twenty-Sixth Supplemental Indenture a valid
agreement of the Issuer and the Trustee and a valid supplement to the Original Indenture have been
done;

NOW, THEREFORE, for and in consideration of the premises and the purchase of the 2018 Notes to
be issued hereunder by Holders thereof, the Issuer and the Trustee mutually covenant and agree, for
the equal and proportionate benefit of the respective Holders from time to time of the 2018 Notes,
as follows:

ARTICLE I

STANDARD PROVISIONS; DEFINITIONS

SECTION 1.01. Standard Provisions. The Original Indenture together with this Twenty-Sixth
Supplemental Indenture and all previous indentures supplemental thereto entered into pursuant to
the applicable terms thereof are hereinafter sometimes collectively referred to as the “Indenture.”
All capitalized terms which are used herein and not otherwise defined herein are defined in the
Original Indenture and are used herein with the same meanings as in the Original Indenture.

SECTION 1.02. Definitions.

(a) The following terms have the meanings set forth in the Sections hereof set forth below:

	 	 	 	 	 
	Term	 	Section
	Applicable Premium

	 	 	2.04	 
	Change of Control Date

	 	 	3.01	 
	Change of Control Purchase Notice

	 	 	3.01	(b)
	Change of Control Purchase Price

	 	 	3.01	 
	Depositary

	 	Article IX

	DTC

	 	 	2.03	 
	Events of Default

	 	 	5.01	 
	Global Note

	 	Article IX

	Indenture

	 	 	1.01; 2.04	 
	Interest Payment Date

	 	 	2.03	 
	Issuer

	 	Preamble; 2.03

	Lien

	 	 	4.02	 
	Original Indenture

	 	Recitals

	Original Issue Date

	 	 	2.03	 
	Place of Payment

	 	 	2.03	 
	Purchase Date

	 	3.01(a)(iii)

	Record Date

	 	 	2.03	 
	Required Repurchase

	 	 	3.01	 
	Securities

	 	Recitals

	Stated Maturity

	 	 	2.01(a); 2.03	 
	Treasury Rate

	 	 	2.04	 
	Trustee

	 	Preamble; 2.04

	2018 Notes

	 	Recitals; 2.04

(b) Section 1.1 of the Original Indenture is amended to insert the new definitions solely
applicable to the 2018 Notes and to replace, solely with respect to the 2018 Notes (but not with
respect to any other series of Securities), any existing definitions (as applicable) in the
Original Indenture, in the appropriate alphabetical sequence, as follows:

“Business Day” means any day on which banking institutions in New York, New York are not
authorized or required by law or regulation to close.

“Capital Lease Obligation” of a Person means any obligation that is required to be classified
and accounted for as a capital lease on the face of a balance sheet of such Person prepared in
accordance with generally accepted accounting principles; the amount of such obligation shall be
the capitalized amount thereof, determined in accordance with generally accepted accounting
principles; the stated maturity thereof shall be the date of the last payment of rent or any other
amount due under such lease prior to the first date upon which such lease may be terminated by the
lessee without payment of a penalty; and such obligation shall be deemed secured by a Lien on any
property or assets to which such lease relates.

“Capital Stock” means any and all shares, interests, rights to purchase, warrants, options,
participations or other equivalents of or interests in (however designated) corporate stock,
including any Preferred Stock or Letter Stock.

“Change of Control” means the occurrence of any of the following events: (1) any “person” or
“group” (as such terms are used in Sections 13(d) and 14(d) of the Exchange Act or any successor
provisions to either of the foregoing) becomes the “beneficial owners” (as used in Rules 13d-3 and
13d-5 under the Exchange Act, except that a person or group will be deemed to have “beneficial
ownership” of all shares that any such person or group has the right to acquire, whether such right
is exercisable immediately or only after the passage of time), directly or indirectly, of a
majority of the total voting power of the Voting Stock of the Issuer, whether as a result of the
issuance of securities of the Issuer, any merger, consolidation, liquidation or dissolution of the
Issuer or otherwise; (2) the sale, transfer, assignment, lease, conveyance or other disposition,
directly or indirectly, of all or substantially all the assets of the Issuer and its subsidiaries,
considered as a whole (other than a disposition of such assets as an entirety or virtually as an
entirety to a wholly-owned subsidiary) shall have occurred, or the Issuer merges, consolidates or
amalgamates with or into any other Person or any other Person merges, consolidates or amalgamates
with or into the Issuer, in any such event pursuant to a transaction in which the outstanding
Voting Stock of the Issuer is reclassified into or exchanged for cash, securities or other
property, other than any such transaction where (a) the outstanding Voting Stock of the Issuer is
reclassified into or exchanged for other Voting Stock of the Issuer or for Voting Stock of the
surviving corporation and (b) the holders of the Voting Stock of the Issuer immediately prior to
such transaction own, directly or indirectly, a majority of the Voting Stock of the Issuer or the
surviving corporation immediately after such transaction and in substantially the same proportion
as before the transaction; (3) during any period, individuals who at the beginning of such period
constituted the board of directors of the Issuer (together with any new directors whose election or
appointment by such board of directors or whose nomination for election by the stockholders of the
Issuer was approved by a vote of a majority of the directors then still in office who were either
directors at the beginning of such period or whose election or nomination for election was
previously so approved) cease for any reason to constitute a majority of the board of directors of
the Issuer then in office; or (4) the stockholders of the Issuer shall have approved any plan of
liquidation or dissolution of the Issuer.

“Change of Control Repurchase Event” means the occurrence of both a Change of Control and a
Rating Decline.

“Consolidated Assets” means, at any date of determination, the aggregate assets of the Issuer
and its Consolidated Subsidiaries determined on a consolidated basis in accordance with generally
accepted accounting principles.

“Consolidated Current Liabilities” means, for any period, the aggregate amount of liabilities
of the Issuer and its Consolidated Subsidiaries which may properly be classified as current
liabilities (including taxes accrued as estimated), after (i) eliminating all inter-company items
between the Issuer and any Consolidated Subsidiary and (ii) deducting all current maturities of
long-term Indebtedness, all as determined in accordance with generally accepted accounting
principles.

“Consolidated Net Tangible Assets” means, for any period, the total amount of assets (less
accumulated depreciation or amortization, allowances for doubtful receivables, other applicable
reserves and other properly deductible items) as set forth on the most recently available quarterly
or annual consolidated balance sheet of the Issuer and its Consolidated Subsidiaries, determined on
a consolidated basis in accordance with generally accepted accounting principles, and after giving
effect to purchase accounting and after deducting therefrom, to the extent otherwise included, the
amounts of: (i) Consolidated Current Liabilities; (ii) minority interests in Consolidated
Subsidiaries held by Persons other than the Issuer or a Restricted Subsidiary; (iii) excess of cost
over fair value of assets of businesses acquired, as determined in good faith by the Board of
Directors as evidenced by resolutions of the Board of Directors; (iv) any revaluation or other
write-up in value of assets subsequent to December 31, 1996, as a result of a change in the method
of valuation in accordance with generally accepted accounting principles; (v) unamortized debt
discount and expenses and other unamortized deferred charges, goodwill, patents, trademarks,
service marks, trade names, copyrights, licenses, organization or developmental expenses and other
intangible items; (vi) treasury stock; and (vii) any cash set apart and held in a sinking or other
analogous fund established for the purpose of redemption or other retirement of Capital Stock to
the extent such obligation is not reflected in Consolidated Current Liabilities.

“Consolidated Subsidiary” means any Subsidiary whose accounts are or are required to be
consolidated with the accounts of the Issuer in accordance with generally accepted accounting
principles.

“Consumers” means Consumers Energy Company, a Michigan corporation and wholly-owned Subsidiary
of the Issuer.

“Enterprises” means CMS Enterprises Company, a Michigan corporation and wholly-owned
Subsidiary of the Issuer.

“Exchange Act” means the Securities Exchange Act of 1934, as amended from time to time, and
any successor legislation.

“Indebtedness” of any Person means, without duplication:

(i) the principal of and premium (if any) in respect of (A) indebtedness of such Person for
money borrowed and (B) indebtedness evidenced by notes, debentures, bonds or other similar
instruments for the payment of which such Person is responsible or liable;

(ii) all Capital Lease Obligations of such Person;

(iii) all obligations of such Person issued or assumed as the deferred purchase price of
property, all conditional sale obligations and all obligations under any title retention agreement
(but excluding trade accounts payable arising in the ordinary course of business);

(iv) all obligations of such Person for the reimbursement of any obligor on any letter of
credit, bankers’ acceptance or similar credit transaction (other than obligations with respect to
letters of credit securing obligations (other than obligations described in clauses (i) through
(iii) above) entered into in the ordinary course of business of such Person to the extent such
letters of credit are not drawn upon or, if and to the extent drawn upon, such drawing is
reimbursed no later than the third Business Day following receipt by such Person of a demand for
reimbursement following payment on the letter of credit);

(v) all obligations of the type referred to in clauses (i) through (iv) above of other Persons
and all dividends of other Persons for the payment of which, in either case, such Person is
responsible or liable as obligor, guarantor or otherwise; and

(vi) all obligations of the type referred to in clauses (i) through (v) above of other Persons
secured by any Lien on any property or asset of such Person (whether or not such obligation is
assumed by such Person), the amount of such obligation being deemed to be the lesser of the value
of such property or assets or the amount of the obligation so secured.

“Investment Grade” means BBB- or higher by S&P and Baa3 or higher by Moody’s, or the
equivalent of such ratings by S&P or Moody’s or, if either S&P or Moody’s shall not make a rating
on the 2018 Notes publicly available, another Rating Agency.

“Letter Stock”, as applied to the Capital Stock of any corporation, means Capital Stock of any
class or classes (however designated) which is intended to reflect the separate performance of
certain of the businesses or operations conducted by such corporation or any of its subsidiaries.

“Moody’s” means Moody’s Investors Service, Inc.

“Paying Agent” means any Person authorized by the Issuer to pay the principal of (and premium,
if any) or interest on any of the 2018 Notes on behalf of the Issuer. Initially, the Paying Agent
shall be the Trustee.

“Person” means any individual, corporation, partnership, limited liability company, joint
venture, association, joint-stock company, trust, unincorporated organization, government or any
agency or political subdivision thereof, or any other entity.

“Predecessor 2018 Note” of any particular 2018 Note means every previous 2018 Note evidencing
all or a portion of the same debt as that evidenced by such particular 2018 Note; and, for the
purposes of the definition, any 2018 Note authenticated and delivered under Section 2.9 of the
Original Indenture in exchange for or in lieu of a mutilated, destroyed, lost or stolen 2018 Note
shall be deemed to evidence the same debt as the mutilated, destroyed, lost or stolen 2018 Note.

“Preferred Stock”, as applied to the Capital Stock of any corporation, means Capital Stock of
any class or classes (however designated) that is preferred as to the payment of dividends, or as
to the distribution of assets upon any voluntary or involuntary liquidation or dissolution of such
corporation, over shares of Capital Stock of any other class of such corporation.

“Rating Agency” means each of S&P and Moody’s or, if S&P or Moody’s or both shall not make a
rating on the 2018 Notes publicly available, a nationally recognized statistical rating
organization or organizations, as the case may be, selected by the Issuer (as certified by a
resolution of the Issuer’s board of directors), which shall be substituted for S&P or Moody’s, or
both, as the case may be.

“Rating Decline” means the rating of the 2018 Notes shall be decreased by one or more
gradations (including gradations within categories as well as between rating categories) by each of
the Rating Agencies on any date from the date of the public notice of an arrangement that could
result in a Change of Control until the end of the 30-day period following public notice of the
occurrence of the Change of Control (which 30-day period shall be extended so long as the rating of
the 2018 Notes is under publicly announced consideration for possible downgrade by either of the
Rating Agencies; provided, that the other Rating Agency has either downgraded, or publicly
announced that it is considering downgrading, the 2018 Notes); provided, however, that if the
rating of the 2018 Notes by each of the Rating Agencies is Investment Grade, then “Rating Decline”
means the rating of the 2018 Notes shall be decreased by one or more gradations (including
gradations within categories as well as between rating categories) by each of the Rating Agencies
such that the rating of the 2018 Notes by each of the Rating Agencies falls below Investment Grade
on any date from the date of the public notice of an arrangement that could result in a Change of
Control until the end of the 30-day period following public notice of the occurrence of the Change
of Control (which 30-day period shall be extended so long as the rating of the 2018 Notes is under
publicly announced consideration for possible downgrade by either of the Rating Agencies; provided,
that the other Rating Agency has either downgraded, or publicly announced that it is considering
downgrading, the 2018 Notes).

“Restricted Subsidiary” means any Subsidiary (other than Consumers and its Subsidiaries) of
the Issuer which, as of the date of the Issuer’s most recent quarterly consolidated balance sheet,
constituted at least 10% of the total Consolidated Assets of the Issuer and its Consolidated
Subsidiaries and any other Subsidiary which from time to time is designated a Restricted Subsidiary
by the Board of Directors; provided that no Subsidiary may be designated a Restricted Subsidiary
if, immediately after giving effect thereto, an Event of Default or event that, with the lapse of
time or giving of notice or both, would constitute an Event of Default would exist, and (i) any
such Subsidiary so designated as a Restricted Subsidiary must be organized under the laws of the
United States or any State thereof, (ii) more than 80% of the Voting Stock of such Subsidiary must
be owned of record and beneficially by the Issuer or a Restricted Subsidiary and (iii) such
Restricted Subsidiary must be a Consolidated Subsidiary.

“S&P” means Standard & Poor’s Ratings Services, a division of The McGraw-Hill Companies, Inc.

“Securities Act” means the Securities Act of 1933, as amended from time to time, and any
successor legislation.

“Support Obligations” means, for any Person, without duplication, any financial obligation,
contingent or otherwise, of such Person guaranteeing or otherwise supporting any debt or other
obligation of any other Person in any manner, whether directly or indirectly, and including,
without limitation, any obligation of such Person, direct or indirect, (i) to purchase or pay (or
advance or supply funds for the purchase or payment of) such debt or to purchase (or to advance or
supply funds for the purchase of) any security for the payment of such debt, (ii) to purchase
property, securities or services for the purpose of assuring the owner of such debt of the payment
of such debt, (iii) to maintain working capital, equity capital, available cash or other financial
statement condition of the primary obligor so as to enable the primary obligor to pay such debt,
(iv) to provide equity capital under or in respect of equity subscription arrangements (to the
extent that such obligation to provide equity capital does not otherwise constitute debt), or (v)
to perform, or arrange for the performance of, any non-monetary obligations or non-funded debt
payment obligations of the primary obligor.

“Voting Stock” means securities of any class or classes the holders of which are ordinarily,
in the absence of contingencies, entitled to vote for corporate directors (or persons performing
similar functions).

ARTICLE II

DESIGNATION AND TERMS OF THE 2018 NOTES; FORMS

SECTION 2.01. Establishment of Series.

(a) There is hereby created a series of Securities to be known and designated as the “5.05%
Senior Notes due 2018” to be issued in aggregate principal amount of $250,000,000. Additional
Securities, without limitation as to amount, having substantially the same terms as the 2018 Notes
(except a different issue date, a different issue price and bearing interest from the last Interest
Payment Date to which interest has been paid or duly provided for on the 2018 Notes, and, if no
interest has been paid, from November 19, 2010), may also be issued by the Issuer pursuant to the
Indenture without the consent of the existing Holders of the 2018 Notes; provided, that such
additional Securities must be part of the same issue as the 2018 Notes for United States federal
income tax purposes. Such additional Securities shall be part of the same series as the 2018
Notes. The “Stated Maturity” of the 2018 Notes is February 15, 2018; the principal amount of the
2018 Notes shall be payable on such date unless the 2018 Notes are earlier redeemed or purchased in
accordance with the terms of the Indenture.

(b) The 2018 Notes will bear interest from the Original Issue Date, or from the most recent
date to which interest has been paid or duly provided for, at the rate of 5.05% per annum stated
therein until the principal thereof is paid or made available for payment. Interest will be
payable semi-annually on each Interest Payment Date and at Maturity, as provided in the form of the
2018 Note in Section 2.03 and Section 2.04 hereof.

(c) The Record Date referred to in Section 2.3(f)(4) of the Original Indenture for the payment
of the interest on any 2018 Note payable on any Interest Payment Date (other than on the Stated
Maturity) shall be the February 1 and August 1 next preceding the relevant Interest Payment Date
(whether or not a Business Day) except that interest payable on the Stated Maturity shall be paid
to the Person to whom the principal amount is paid.

(d) The payment of the principal of, and premium (if any) and interest on, the 2018 Notes
shall not be secured by a security interest in any property.

(e) The 2018 Notes shall be redeemable at the option of the Issuer, in whole or in part, at
any time and from time to time, upon not less than 30, nor more than 60 days’ notice at a
redemption price equal to 100% of the principal amount of such 2018 Notes being redeemed plus the
Applicable Premium, if any, thereon at the time of redemption, together with accrued and unpaid
interest, if any, thereon to, but not including, the redemption date. In no event will the
redemption price ever be less than 100% of the principal amount of the 2018 Notes plus accrued
interest, if any, thereon to the redemption date. The 2018 Notes shall be purchased by the Issuer
at the option of the Holders thereof as provided in Article III hereof.

(f) The 2018 Notes shall not be convertible.

(g) The 2018 Notes will not be subordinated to the payment of Senior Debt.

(h) The Issuer will not pay any additional amounts on the 2018 Notes held by a Person who is
not a U.S. person (as defined in Regulation S under the Securities Act) in respect of any tax,
assessment or government charge withheld or deducted.

(i) The events specified in Events of Default with respect to the 2018 Notes shall include the
events specified in Article VI hereof. In addition to the covenants set forth in Article Three of
the Original Indenture, the Holders of the 2018 Notes shall have the benefit of the covenants of
the Issuer set forth in Article IV hereof. The provisions of Section 9.1 and Section 9.2 of the
Original Indenture shall be amended and restated solely with respect to the 2018 Notes as specified
in Article V hereof.

(j) The 2018 Notes are issuable only in registered form without coupons in minimum
denominations of $2,000 and any integral multiple of $1,000 in excess thereof.

(k) The provisions of Article VII, Article VIII and Article IX hereof shall apply to the 2018
Notes as specified therein.

SECTION 2.02. Forms Generally. The 2018 Notes and Trustee’s certificate of authentication
shall be in substantially the form set forth in this Article II, with such appropriate insertions,
omissions, substitutions and other variations as are required or permitted by the Indenture, and
may have such letters, numbers or other marks of identification and such legends or endorsements
placed thereon as may be required to comply with the rules of any securities exchange or as may,
consistently herewith, be determined by the officers executing such 2018 Notes, as evidenced by
their execution thereof.

The definitive 2018 Notes shall be printed, lithographed or engraved on steel engraved borders
or may be produced in any other manner, all as determined by the officers executing such 2018
Notes, as evidenced by their execution thereof.

SECTION 2.03. Form of Face of 2018 Note.

THIS SECURITY IS A REGISTERED GLOBAL SECURITY WITHIN THE MEANING OF THE INDENTURE HEREINAFTER
REFERRED TO AND IS REGISTERED IN THE NAME OF A DEPOSITARY OR A NOMINEE OF A DEPOSITARY. THIS
SECURITY IS EXCHANGEABLE FOR SECURITIES REGISTERED IN THE NAME OF A PERSON OTHER THAN THE
DEPOSITARY OR ITS NOMINEE ONLY IN THE LIMITED CIRCUMSTANCES DESCRIBED IN THE INDENTURE AND MAY NOT
BE TRANSFERRED EXCEPT AS A WHOLE BY THE DEPOSITARY TO A NOMINEE OF THE DEPOSITARY OR BY A NOMINEE
OF THE DEPOSITARY TO THE DEPOSITARY OR ANOTHER NOMINEE OF THE DEPOSITARY.

Unless this Global Note is presented by an authorized representative of The Depository Trust
Company, a New York corporation (“DTC”), to CMS Energy Corporation or its agent for registration of
transfer, exchange or payment, and any certificate issued is registered in the name of a nominee of
DTC or in such other name as is requested by an authorized representative of DTC (and any payment
is made to such nominee of DTC or to such other entity as is requested by an authorized
representative of DTC), ANY TRANSFER, PLEDGE OR OTHER USE HEREOF FOR VALUE OR OTHERWISE BY OR TO
ANY PERSON IS WRONGFUL inasmuch as the registered owner hereof has an interest herein.

CMS ENERGY CORPORATION

5.05% SENIOR NOTES DUE 2018

No. 1 $250,000,000

CUSIP No.: 125896BG4

ISIN No.: US125896BG45

CMS Energy Corporation, a corporation duly organized and existing under the laws of the State
of Michigan (herein called the “Issuer”, which term includes any successor Person under the
Indenture hereinafter referred to), for value received, hereby promises to pay to CEDE & CO., or
registered assigns, the principal sum of Two Hundred Fifty Million Dollars on February 15, 2018
(“Stated Maturity”) and to pay interest thereon from November 19, 2010 (the “Original Issue Date”)
or from the most recent Interest Payment Date to which interest has been paid or duly provided for,
semi-annually in arrears on February 15 and August 15 in each year, commencing on August 15, 2011
(each an “Interest Payment Date”), to the Persons in whose names the 2018 Notes are registered at
5:00 p.m., New York City time, on the February 1 and August 1 next preceding the relevant Interest
Payment Date (each a “Record Date”), and on the Stated Maturity, to the Person to whom the
principal amount is paid, at the rate of 5.05% per annum, until the principal hereof is paid or
made available for payment. The amount of interest payable on any Interest Payment Date shall be
computed on the basis of a 360-day year of twelve 30-day months. Any such interest not so
punctually paid or duly provided for will forthwith cease to be payable to the Holder on such
Record Date and may either be paid to the Person in whose name this 2018 Note (or one or more
Predecessor 2018 Notes) is registered at 5:00 p.m., New York City time, on a subsequent record date
(which shall be not less than five Business Days prior to the date of payment of such defaulted
interest) for the payment of such defaulted interest to be fixed by the Trustee, notice whereof
shall be given to Holders of 2018 Notes not less than 15 calendar days preceding such subsequent
Record Date.

Payment of the principal of (and premium, if any) and interest on this 2018 Note will be made
at the office or agency of the Issuer maintained for that purpose in New York, New York (the “Place
of Payment”), in such coin or currency of the United States of America as at the time of payment is
legal tender for payment of public and private debts; provided, however, that at the option of the
Issuer payment of interest (other than interest payable at Maturity) may be made by check mailed to
the address of the Person entitled thereto as such address shall appear in the Security Register or
by wire transfer to an account designated by such Person not later than ten days prior to the date
of such payment.

Reference is hereby made to the further provisions of this 2018 Note set forth on the reverse
hereof, which further provisions shall for all purposes have the same effect as if set forth at
this place.

Unless the certificate of authentication hereon has been executed by the Trustee referred to
on the reverse hereof by manual signature, this 2018 Note shall not be entitled to any benefit
under the Indenture or be valid or obligatory for any purpose.

IN WITNESS WHEREOF, the Issuer has caused this instrument to be duly executed under its
corporate seal.

Dated:

CMS ENERGY CORPORATION

By

Its:

By

Its:

SECTION 2.04. Form of Reverse of 2018 Note.

This 5.05% Senior Note due 2018 is one of a duly authorized issue of securities of the Issuer
(herein called the “2018 Notes”), issued and to be issued under an Indenture, dated as of September
15, 1992 (as supplemented by the Twenty-Sixth Supplemental Indenture, dated as of November 19, 2010
and as further amended or supplemented from time to time, the “Indenture”), between the Issuer and
The Bank of New York Mellon, a New York banking corporation (ultimate successor to NBD Bank,
National Association), as Trustee (herein called the “Trustee”, which term includes any successor
trustee under the Indenture), to which Indenture and all indentures supplemental thereto reference
is hereby made for a statement of the respective rights, limitations of rights, duties and
immunities thereunder of the Issuer, the Trustee, and the Holders of the 2018 Notes and of the
terms upon which the 2018 Notes are, and are to be, authenticated and delivered. This 2018 Note is
one of the series designated on the face hereof, issued in an initial aggregate principal amount of
$250,000,000. Additional Securities, without limitation as to amount, having substantially the
same terms as the 2018 Notes (except a different issue date, a different issue price and bearing
interest from the last Interest Payment Date to which interest has been paid or duly provided for
on the 2018 Notes, and, if no interest has been paid, from November 19, 2010), may also be issued
by the Issuer pursuant to the Indenture without the consent of the existing Holders of the 2018
Notes; provided, that such additional Securities must be part of the same issue as the 2018 Notes
for United States federal income tax purposes. Such additional Securities shall be part of the
same series as the 2018 Notes.

No sinking fund is provided for the 2018 Notes.

The 2018 Notes are subject to redemption at the option of the Issuer, in whole or in part,
upon not less than 30 nor more than 60 days’ notice as provided in the Indenture at any time and
from time to time, at a redemption price equal to 100% of the principal amount of such 2018 Notes
being redeemed plus the Applicable Premium, if any, thereon at the time of redemption, together
with accrued and unpaid interest, if any, thereon to, but not including, the redemption date, but
interest installments whose Stated Maturity is on or prior to such redemption date will be payable
to the Holder of record at the close of business on the relevant Record Date referred to on the
face hereof, all as provided in the Indenture. In no event will the redemption price ever be less
than 100% of the principal amount of the 2018 Notes plus accrued interest to the redemption date.

The following definitions are used to determine the Applicable Premium:

“Applicable Premium” means, with respect to a 2018 Note (or portion thereof) being redeemed at
any time, the excess of (A) the present value at such time of the principal amount of such 2018
Note (or portion thereof) being redeemed plus all interest payments due on such 2018 Note (or
portion thereof) after the redemption date, which present value shall be computed using a discount
rate equal to the Treasury Rate plus 50 basis points, over (B) the principal amount of such 2018
Note (or portion thereof) being redeemed at such time. For purposes of this definition, the
present values of the interest and principal payments will be determined in accordance with
generally accepted principles of financial analysis.

“Treasury Rate” means the yield to maturity at the time of computation of United States
Treasury securities with a constant maturity (as compiled and published in the most recent Federal
Reserve Statistical Release H.15(519) which has become publicly available at least two Business
Days prior to the redemption date or, in the case of defeasance, prior to the date of deposit (or,
if such Statistical Release is no longer published, any publicly available source of similar market
data)) most nearly equal to the then remaining average life to stated maturity of the 2018 Notes;
provided, however, that if the average life to stated maturity of the 2018 Notes is not equal to
the constant maturity of a United States Treasury security for which a weekly average yield is
given, the Treasury Rate shall be obtained by linear interpolation (calculated to the nearest
one-twelfth of a year) from the weekly average yields of United States Treasury securities for
which such yields are given.

If a Change of Control Repurchase Event occurs, the Issuer shall notify the Holder of this
2018 Note of such occurrence and such Holder shall have the right to require the Issuer to make a
Required Repurchase of all or any part of this 2018 Note at a Change of Control Purchase Price
equal to 101% of the principal amount of this 2018 Note to be so purchased as more fully provided
in the Indenture and subject to the terms and conditions set forth therein. In the event of a
Required Repurchase of only a portion of this 2018 Note, a new 2018 Note or 2018 Notes for the
unrepurchased portion hereof will be issued in the name of the Holder hereof upon the cancellation
hereof.

If an Event of Default with respect to this 2018 Note shall occur and be continuing, the
principal of this 2018 Note may be declared due and payable in the manner and with the effect
provided in the Indenture.

In any case where any Interest Payment Date, redemption date, repurchase date, Stated Maturity
or Maturity of any 2018 Note shall not be a Business Day, then (notwithstanding any other provision
of the Indenture or this 2018 Note) payment of interest or principal (and premium, if any) need not
be made on such date, but may be made on the next succeeding Business Day with the same force and
effect as if made on the Interest Payment Date, redemption date, repurchase date or Stated Maturity
or at Maturity; provided that no interest shall accrue on the amount so payable for the period from
and after such Interest Payment Date, redemption date, repurchase date, Stated Maturity or
Maturity, as the case may be, to such Business Day.

The Trustee and the Paying Agent shall return to the Issuer upon written request any money or
property held by them for the payment of any amount with respect to the 2018 Notes that remains
unclaimed for two years, provided, however, that the Trustee or such Paying Agent, before being
required to make any such return, shall at the expense of the Issuer cause to be published once in
a newspaper of general circulation in The City of New York or mail to each such Holder notice that
such money or property remains unclaimed and that, after a date specified therein, which shall not
be less than 30 days from the date of such publication or mailing, any unclaimed money or property
then remaining shall be returned to the Issuer. After return to the Issuer, Holders entitled to
the money or property must look to the Issuer for payment as general creditors unless an applicable
abandoned property law designates another Person.

The Indenture contains provisions for defeasance at any time of (i) the entire indebtedness of
this 2018 Note or (ii) certain restrictive covenants and Events of Default with respect to this
2018 Note, in each case upon compliance with certain conditions set forth therein.

The Indenture permits, with certain exceptions as therein provided, the amendment thereof and
the modification of the rights and obligations of the Issuer and the rights of the Holders of all
outstanding 2018 Notes under the Indenture at any time by the Issuer and the Trustee with the
consent of the Holders of not less than a majority in principal amount of Securities of all series
(including the 2018 Notes) then outstanding and affected (voting as one class).

The Indenture permits the Holders of a majority in principal amount of Securities of all
series at the time outstanding with respect to which a default shall have occurred and be
continuing (voting as one class) to waive on behalf of the Holders of all outstanding Securities of
such series any past default by the Issuer, provided that no such waiver may be made with respect
to a default in the payment of the principal of or the interest on any Security of such series, the
default in the payment of the redemption price or Change of Control Purchase Price with respect to
the 2018 Notes, or the default by the Issuer in respect of certain covenants or provisions of the
Indenture, the modification or amendment of which must be consented to by the Holder of each
outstanding Security of each series affected.

As set forth in, and subject to, the provisions of the Indenture, no Holder of any 2018 Note
will have any right to institute any proceeding with respect to the Indenture or for any remedy
thereunder, unless such Holder shall have previously given to the Trustee written notice of a
continuing Event of Default, the Holders of not less than 25% in principal amount of the
outstanding Securities of each affected series (voting as one class) shall have made written
request, and offered reasonable indemnity against costs, expenses and liabilities, to the Trustee
to institute such proceeding as trustee, and the Trustee shall not have received from the Holders
of a majority in principal amount of the outstanding Securities of each affected series (voting as
one class) a direction inconsistent with such request and shall have failed to institute such
proceeding within 60 days; provided, however, that such limitations do not apply to a suit
instituted by the Holder hereof for the enforcement of payment of the principal of (and premium, if
any) or any interest on this 2018 Note on or after the respective due dates expressed herein.

No reference herein to the Indenture and no provision of this 2018 Note or of the Indenture
shall alter or impair the obligation of the Issuer, which is absolute and unconditional, to pay the
principal of and any premium and interest on this 2018 Note at the times, place and rate, and in
the coin or currency, herein prescribed.

As provided in the Indenture and subject to certain limitations therein set forth, the
transfer of this 2018 Note is registrable in the Security Register, upon surrender of this 2018
Note for registration of transfer at the office or agency of the Issuer in any place where the
principal of and any premium and interest on this 2018 Note are payable, duly endorsed by, or
accompanied by a written instrument of transfer in form satisfactory to the Issuer and the Security
Registrar duly executed by, the Holder hereof or such Holder’s attorney duly authorized in writing,
and thereupon one or more new 2018 Notes of this series and of like tenor, of authorized
denominations and for the same aggregate principal amount, will be issued to the designated
transferee or transferees.

The 2018 Notes are issuable only in registered form without coupons in minimum denominations
of $2,000 and any integral multiple of $1,000 in excess thereof. As provided in the Indenture and
subject to certain limitations therein set forth, 2018 Notes are exchangeable for a like aggregate
principal amount of 2018 Notes and of like tenor of a different authorized denomination, as
requested by the Holder surrendering the same.

No service charge shall be made for any such registration of transfer or exchange, but the
Issuer may require payment of a sum sufficient to cover any tax or other governmental charge
payable in connection therewith.

The Issuer shall not be required to (i) issue, exchange or register the transfer of this 2018
Note for a period of 15 days next preceding the mailing of the notice of redemption of 2018 Notes
or (ii) exchange or register the transfer of any 2018 Note or any portion thereof selected, called
or being called for redemption, except in the case of any 2018 Note to be redeemed in part, the
portion thereof not so to be redeemed.

Prior to due presentment of this 2018 Note for registration of transfer, the Issuer, the
Trustee and any agent of the Issuer or the Trustee may treat the Person in whose name this 2018
Note is registered as the owner hereof for all purposes, whether or not this 2018 Note be overdue,
and neither the Issuer, the Trustee nor any such agent shall be affected by notice to the contrary.

All terms used in this 2018 Note without definition which are defined in the Indenture shall
have the meanings assigned to them in the Indenture. In case of any conflict between this 2018
Note and the Indenture, the provisions of the Indenture shall control.

SECTION 2.05. Form of Trustee’s Certificate of Authentication. The Trustee’s certificate of
authentication shall be in substantially the following form:

This is one of the Securities of the series designated herein referred to in the
within-mentioned Indenture.

THE BANK OF NEW YORK MELLON,

as Trustee

By

Authorized Officer

SECTION 2.06. Rights of Trustee. The Trustee shall not be deemed to have notice, or be
charged with knowledge, of any event requiring notice under the Indenture unless the Trustee shall
have received from the Issuer or other requisite party such notice in writing.

ARTICLE III

CHANGE OF CONTROL

SECTION 3.01. Change of Control. Upon the occurrence of a Change of Control Repurchase Event
(the effective date of such Change of Control Repurchase Event being the “Change of Control Date”),
each Holder of a 2018 Note shall have the right to require that the Issuer repurchase (a “Required
Repurchase”) all or any part of such Holder’s 2018 Note at a repurchase price payable in cash equal
to 101% of the principal amount of such 2018 Note plus accrued interest, if any, to the Purchase
Date (the “Change of Control Purchase Price”).

(a) Within 30 days following the Change of Control Date, the Issuer shall mail a notice to
each Holder with a copy to the Trustee stating:

(i) that a Change of Control Repurchase Event has occurred and that such Holder has the
right to require the Issuer to repurchase all or any part of such Holder’s 2018 Notes at the
Change of Control Purchase Price;

(ii) the Change of Control Purchase Price;

(iii) the date on which any Required Repurchase shall be made (which shall be no
earlier than 60 days nor later than 90 days from the date such notice is mailed) (the
“Purchase Date”);

(iv) the name and address of the Paying Agent; and

(v) the procedures that Holders must follow to cause the 2018 Notes to be repurchased,
which shall be consistent with this Section 3.01 and the Indenture.

(b) Holders electing to have a 2018 Note repurchased must deliver a written notice (the
“Change of Control Purchase Notice”) to the Paying Agent (initially the Trustee) at its corporate
trust office in New York, New York, or any other office of the Paying Agent maintained for such
purposes, not later than 30 days prior to the Purchase Date. The Change of Control Purchase Notice
shall state: (i) the portion of the principal amount of any 2018 Notes to be repurchased, which
portion must be a minimum of $2,000 and in $1,000 integral multiples; (ii) that such 2018 Notes are
to be repurchased by the Issuer pursuant to the change of control provisions of the Indenture; and
(iii) unless the 2018 Notes are represented by one or more Global Notes, the certificate numbers of
the 2018 Notes to be delivered by the Holder thereof for repurchase by the Issuer. Any Change of
Control Purchase Notice may be withdrawn by the Holder by a written notice of withdrawal delivered
to the Paying Agent not later than three Business Days prior to the Purchase Date. The notice of
withdrawal shall state the principal amount and, if applicable, the certificate numbers of the 2018
Notes as to which the withdrawal notice relates and the principal amount of such 2018 Notes, if
any, which remains subject to a Change of Control Purchase Notice.

If a 2018 Note is represented by a Global Note (as described in Article IX hereof), the
Depositary or its nominee will be the Holder of such 2018 Note and therefore will be the only
entity that can elect a Required Repurchase of such 2018 Note. To obtain repayment pursuant to
this Section 3.01 with respect to such 2018 Note, the beneficial owner of such 2018 Note must
provide to the broker or other entity through which it holds the beneficial interest in such 2018
Note (i) the Change of Control Purchase Notice signed by such beneficial owner, and such signature
must be guaranteed by a member firm of a registered national securities exchange or of the
Financial Industry Regulatory Authority, Inc. or a commercial bank or trust company having an
office or correspondent in the United States, and (ii) instructions to such broker or other entity
to notify the Depositary of such beneficial owner’s desire to obtain repayment pursuant to this
Section 3.01. Such broker or other entity will provide to the Paying Agent (i) the Change of
Control Purchase Notice received from such beneficial owner and (ii) a certificate satisfactory to
the Paying Agent from such broker or other entity stating that it represents such beneficial owner.
Such broker or other entity will be responsible for disbursing any payments it receives pursuant
to this Section 3.01 to such beneficial owner.

(c) Payment of the Change of Control Purchase Price for a 2018 Note for which a Change of
Control Purchase Notice has been delivered and not withdrawn is conditioned (except in the case of
a 2018 Note represented by one or more Global Notes) upon delivery of such 2018 Note (together with
necessary endorsements) to the Paying Agent at its office in New York, New York, or any other
office of the Paying Agent maintained for such purpose, at any time (whether prior to, on or after
the Purchase Date) after the delivery of such Change of Control Purchase Notice. Payment of the
Change of Control Purchase Price for such 2018 Note will be made promptly following the later of
the Purchase Date or the time of delivery of such 2018 Note. If the Paying Agent holds, in
accordance with the terms of the Indenture, money sufficient to pay the Change of Control Purchase
Price of such 2018 Note on the Business Day following the Purchase Date, then, on and after such
date, interest will cease accruing, and all other rights of the Holder shall terminate (other than
the right to receive the Change of Control Purchase Price upon delivery of the 2018 Note).

(d) The Issuer shall comply with the provisions of Regulation 14E and any other tender offer
rules under the Exchange Act, which may then be applicable in connection with any offer by the
Issuer to repurchase 2018 Notes at the option of Holders upon a Change of Control Repurchase Event.

(e) No 2018 Note may be repurchased by the Issuer as a result of a Change of Control
Repurchase Event if there has occurred and is continuing an Event of Default (other than a default
in the payment of the Change of Control Purchase Price with respect to the 2018 Notes).

ARTICLE IV

ADDITIONAL COVENANTS OF THE ISSUER

WITH RESPECT TO THE 2018 NOTES

SECTION 4.01. Existence. So long as any of the 2018 Notes are outstanding, subject to
Article Nine of the Original Indenture, the Issuer will do or cause to be done all things necessary
to preserve and keep in full force and effect its corporate existence.

SECTION 4.02. Limitation on Certain Liens. So long as any of the 2018 Notes are outstanding,
the Issuer shall not create, incur, assume or suffer to exist any lien, mortgage, pledge, security
interest, conditional sale, title retention agreement or other charge or encumbrance of any kind,
or any other type of arrangement intended or having the effect of conferring upon a creditor of the
Issuer or any Subsidiary a preferential interest (a “Lien”) upon or with respect to any of its
property of any character, including without limitation any shares of Capital Stock of Consumers or
Enterprises, without making effective provision whereby the 2018 Notes shall (so long as any such
other creditor shall be so secured) be equally and ratably secured (along with any other creditor
similarly entitled to be secured) by a direct Lien on all property subject to such Lien, provided,
however, that the foregoing restrictions shall not apply to:

(i) Liens for taxes, assessments or governmental charges or levies to the extent not
past due;

(ii) pledges or deposits to secure (A) obligations under workmen’s compensation laws or
similar legislation, (B) statutory obligations of the Issuer or (C) Support Obligations;

(iii) Liens imposed by law, such as materialmen’s, mechanics’, carriers’, workmen’s and
repairmen’s Liens and other similar Liens arising in the ordinary course of business
securing obligations which are not overdue or which have been fully bonded and are being
contested in good faith;

(iv) purchase money Liens upon or in property acquired and held by the Issuer in the
ordinary course of business to secure the purchase price of such property or to secure
Indebtedness incurred solely for the purpose of financing the acquisition of any such
property to be subject to such Liens, or Liens existing on any such property at the time of
acquisition, or extensions, renewals or replacements of any of the foregoing for the same or
a lesser amount, provided that no such Lien shall extend to or cover any property other than
the property being acquired and no such extension, renewal or replacement shall extend to or
cover property not theretofore subject to the Lien being extended, renewed or replaced, and
provided, further, that the aggregate principal amount of the Indebtedness at any one time
outstanding secured by Liens permitted by this Section 4.02(iv) shall not exceed
$10,000,000; and

(v) Liens not otherwise permitted by Section 4.02(i) through Section 4.02(iv) hereof
securing Indebtedness of the Issuer; provided that on the date such Liens are created, and
after giving effect to such Indebtedness, the aggregate principal amount at maturity of all
of the secured Indebtedness of the Issuer at such date shall not exceed 10% of Consolidated
Net Tangible Assets at such date.

SECTION 4.03. Reporting. For purposes of Section 4.3(a) of the Original Indenture solely
with respect to the 2018 Notes (but not with respect to any other series of Securities), the
Trustee agrees that documents filed by the Issuer with the Commission via the Commission’s EDGAR
system (or any successor thereto) will constitute filing of the same with the Trustee as of the
time such documents are so filed.

ARTICLE V

CONSOLIDATION, MERGER AND TRANSFER OF PROPERTY

SECTION 5.01. Limitation on Consolidation, Merger and Transfer. Section 9.1 of the Original
Indenture is hereby amended and restated solely with respect to the 2018 Notes (but not with
respect to any other series of Securities) as follows, and all references in the Original Indenture
to Section 9.1 thereof and to the provisions specified therein shall, with respect to the 2018
Notes, be deemed to be references to this Section 5.01 and to the provisions specified herein,
respectively.

“Nothing contained in the Indenture or in any of the 2018 Notes shall prevent any
consolidation or merger of the Issuer with or into any other Person or Persons (whether or not
affiliated with the Issuer), or successive consolidations or mergers in which the Issuer or its
successor or successors shall be a party or parties, or shall prevent any conveyance, transfer or
lease of the property of the Issuer as an entirety or substantially as an entirety, to any other
Person (whether or not affiliated with the Issuer); provided, however, that:

(a) in case the Issuer shall consolidate with or merge into another Person or convey, transfer
or lease its properties and assets as an entirety or substantially as an entirety to any Person,
the entity formed by such consolidation or into which the Issuer is merged or the Person that
acquires by conveyance or transfer, or that leases, the properties and assets of the Issuer as an
entirety or substantially as an entirety shall be a corporation or a limited liability company
organized and existing under the laws of the United States of America, any state thereof or the
District of Columbia and shall expressly assume, by an indenture (or indentures, if at such time
there is more than one Trustee) supplemental to the Indenture, executed by the successor Person and
delivered to the Trustee, in form satisfactory to the Trustee, the due and punctual payment of the
principal of and any premium and interest on the 2018 Notes and the performance of every obligation
in the Indenture and the outstanding 2018 Notes on the part of the Issuer to be performed or
observed;

(b) immediately after giving effect to such transaction, no Event of Default or event that,
after notice or lapse of time, or both, would become an Event of Default, shall have occurred and
be continuing; and

(c) either the Issuer or the successor Person shall have delivered to the Trustee an Officers’
Certificate and an Opinion of Counsel, each stating that such consolidation, merger, conveyance,
transfer or lease and, if a supplemental indenture is required in connection with such transaction,
such supplemental indenture complies with the provisions of the Indenture and all conditions
precedent therein relating to such transaction.”

SECTION 5.02. Successor Person Substituted for the Issuer. Section 9.2 of the Original
Indenture is hereby amended and restated solely with respect to the 2018 Notes (but not with
respect to any other series of Securities) as follows, and all references in the Original Indenture
to Section 9.2 thereof and to the provisions specified therein shall, with respect to the 2018
Notes, be deemed to be references to this Section 5.02 and to the provisions specified herein,
respectively.

“Upon any consolidation by the Issuer with or merger of the Issuer into any other Person or
any conveyance, transfer or lease of the properties and assets of the Issuer substantially as an
entirety to any Person in accordance with Section 5.01 hereof, the successor Person formed by such
consolidation or into which the Issuer is merged or to which such conveyance, transfer or lease is
made shall succeed to, and be substituted for, and may exercise every right and power of, the
Issuer under the Indenture with the same effect as if such successor Person had been named as the
Issuer herein; and thereafter, the predecessor Person shall be released from all obligations and
covenants under the Indenture and the 2018 Notes.

In case of any such consolidation, merger, conveyance, transfer or lease, such changes in
phraseology and form (but not in substance) may be made in the 2018 Notes thereafter to be issued
as may be appropriate.”

ARTICLE VI

ADDITIONAL EVENTS OF DEFAULT

WITH RESPECT TO THE 2018 NOTES

SECTION 6.01. Definition. All of the events specified in Section 5.1(a) through Section
5.1(h) of the Original Indenture shall be “Events of Default” with respect to the 2018 Notes.

SECTION 6.02. Amendments to Section 5.1 of the Original Indenture. Solely for the purpose of
determining Events of Default with respect to the 2018 Notes (but not with respect to any other
series of Securities), Section 5.1(e), Section 5.1(f) and Section 5.1(h) of the Original Indenture
shall be amended such that each and every reference in Section 5.1(e) and Section 5.1(f) and the
first two references in Section 5.1(h) of the Original Indenture to the Issuer shall be deemed to
mean either the Issuer or Consumers.

SECTION 6.03. Additional Events of Default. Solely for the purpose of determining Events of
Default with respect to the 2018 Notes (but not with respect to any other series of Securities), an
Event of Default shall also include default in the Issuer’s obligation to redeem the 2018 Notes
after exercising its redemption option pursuant to this Twenty-Sixth Supplemental Indenture.

SECTION 6.04. Additional Waivers of Past Defaults. In addition to those matters set forth in
Section 5.10 of the Original Indenture, solely with respect to the 2018 Notes (but not with respect
to any other series of Securities), approval of the Holders of each outstanding 2018 Note shall be
required to waive any default in any payment of the redemption price or Change of Control Purchase
Price with respect to any 2018 Note.

ARTICLE VII

DISCHARGE OF INDENTURE AND DEFEASANCE

All of the provisions of Article Ten of the Original Indenture shall be applicable to the 2018
Notes. Upon satisfaction by the Issuer of the requirements of Section 10.1(C) of the Original
Indenture, in connection with any covenant defeasance (as provided in Section 10.1(C) of the
Original Indenture), the Issuer shall be released from its obligations under Article Three and
Article Nine of the Original Indenture and under Article IV and Article V hereof with respect to
the 2018 Notes and the omission to comply with such obligations under such Articles upon such
covenant defeasance shall not constitute an Event of Default under the Indenture with respect to
the 2018 Notes.

ARTICLE VIII

MODIFICATION AND WAIVER

SECTION 8.01. Without Consent of Holders. In addition to any permitted amendment or
supplement to the Indenture pursuant to Section 8.1(a), Section 8.1(b), Section 8.1(c), Section
8.1(e) and Section 8.1(f) of the Original Indenture, the Issuer and the Trustee may amend or
supplement the Indenture (to the extent applicable to the 2018 Notes) or the 2018 Notes without
notice to or the consent of any Holder, to:

(a) surrender any right or power conferred upon the Issuer;

(b) comply with the requirements of the Commission in order to effect or maintain the
qualification of the Indenture under the Trust Indenture Act of 1939, as amended; and

(c) add guarantees of obligations under the 2018 Notes.

In addition, Section 8.1(d) of the Original Indenture is hereby amended and restated solely
with respect to the 2018 Notes (but not with respect to any other series of Securities) as follows,
and all references in the Original Indenture to Section 8.1(d) thereof shall, with respect to the
2018 Notes, be deemed to be references to the following provisions of this Section 8.01:

“(d)(1) cure any ambiguity or correct or supplement any inconsistent or otherwise defective
provision contained in the Indenture; provided that such modification or amendment does not
adversely affect the interests of the Holders of the 2018 Notes in any material respect; provided,
further, that any amendment made solely to conform the provisions of the Indenture and the form or
terms of the 2018 Notes to the section entitled “Description of the Notes” as set forth in the
final prospectus supplement related to the offering and sale of the 2018 Notes dated November 16,
2010 will not be deemed to adversely affect the interests of the Holders of the 2018 Notes;

(d)(2) make any provision with respect to matters or questions arising under the Indenture
that the Issuer may deem necessary or desirable and that shall not be inconsistent with provisions
of the Indenture; provided, that such change or modification does not, in the good faith opinion of
the Board of Directors, adversely affect the interests of the Holders of the 2018 Notes in any
material respect;”

SECTION 8.02. With Consent of Holders. In addition to those matters set forth in Section 8.2
of the Original Indenture, solely with respect to the 2018 Notes (but not with respect to any other
series of Securities), no amendment or supplemental indenture to the Indenture shall, without the
consent of the Holder of each 2018 Note affected thereby:

(a) reduce the redemption price or Change of Control Purchase Price of the 2018 Notes;

(b) change the terms applicable to redemption or purchase of the 2018 Notes in a manner
adverse to the Holder; or

(c) change the Issuer’s obligation to maintain an office or agency in New York, New York.

ARTICLE IX

GLOBAL NOTES

The 2018 Notes will be issued initially in the form of one or more Global Notes. “Global
Note” means a registered 2018 Note evidencing one or more 2018 Notes issued to a depositary (the
“Depositary”) or its nominee, in accordance with this Article IX and bearing the legend prescribed
in this Article IX. The Issuer shall execute and the Trustee shall, in accordance with this
Article IX and the Issuer Order with respect to the 2018 Notes, authenticate and deliver one or
more Global Notes in temporary or permanent form that (i) shall represent and shall be denominated
in an aggregate amount equal to the aggregate principal amount of the 2018 Notes to be represented
by such Global Note or Global Notes, (ii) shall be registered in the name of the Depositary for
such Global Note or Global Notes or the nominee of such Depositary, (iii) shall be delivered by the
Trustee to such Depositary or pursuant to such Depositary’s instructions and (iv) shall bear a
legend substantially to the following effect: “Unless this Global Note is presented by an
authorized representative of the Depositary to the Issuer or its agent for registration of
transfer, exchange or payment, and any certificate issued is registered in the name of a nominee of
the Depositary or in such other name as is requested by an authorized representative of the
Depositary (and any payment is made to such nominee of the Depositary or to such other entity as is
requested by an authorized representative of the Depositary), ANY TRANSFER, PLEDGE OR OTHER USE
HEREOF FOR VALUE OR OTHERWISE BY OR TO ANY PERSON IS WRONGFUL inasmuch as the registered owner
hereof has an interest herein.”

Notwithstanding Section 2.8 of the Original Indenture, unless and until it is exchanged in
whole or in part for 2018 Notes in definitive form, a Global Note representing one or more 2018
Notes may not be transferred except as a whole by the Depositary, to a nominee of such Depositary
or by a nominee of such Depositary to such Depositary or another nominee of such Depositary or by
such Depositary or any such nominee to a successor Depositary for 2018 Notes or a nominee of such
successor Depositary.

If at any time the Depositary for the 2018 Notes is unwilling or unable to continue as
Depositary for the 2018 Notes, defaults in the performance of its duties as Depositary or ceases to
be a clearing agency registered under the Exchange Act or other applicable statute or regulation,
the Issuer shall appoint a successor Depositary with respect to the 2018 Notes. If a successor
Depositary for the 2018 Notes is not appointed by the Issuer by the earlier of (x) 90 days from the
date the Issuer receives notice to the effect that the Depositary is unwilling or unable to act, or
the Issuer determines that the Depositary is unable to act, or (y) the effectiveness of the
Depositary’s resignation or failure to fulfill its duties as Depositary, the Issuer will execute,
and the Trustee, upon receipt of an Issuer Order for the authentication and delivery of definitive
2018 Notes, will authenticate and deliver 2018 Notes in definitive form in an aggregate principal
amount equal to the principal amount of the Global Note or Global Notes representing such 2018
Notes in exchange for such Global Note or Global Notes.

If the Issuer so specifies with respect to any 2018 Notes, an owner of a beneficial interest
in a Global Note representing the 2018 Notes may, on terms acceptable to the Issuer and the
Depositary for the Global Note, receive individual 2018 Notes in exchange for the beneficial
interest. In any such instance, an owner of a beneficial interest in a Global Note will be
entitled to physical delivery in definitive form of 2018 Notes represented by the Global Note equal
in principal amount to the beneficial interest, and to have the 2018 Notes registered in its name.
2018 Notes so issued in definitive form will be issued as registered 2018 Notes in minimum
denominations of $2,000 and in $1,000 integral multiples, unless otherwise specified by the Issuer.

Upon the exchange of a Global Note for 2018 Notes in definitive form, such Global Note shall
be cancelled by the Trustee. 2018 Notes in definitive form issued in exchange for a Global Note
pursuant to this Article IX shall be registered in such names and in such authorized denominations
as the Depositary for such Global Note, pursuant to instructions from its direct or indirect
participants or otherwise, shall instruct the Trustee or Security Registrar. The Trustee shall
deliver such 2018 Notes to the Persons in whose names such 2018 Notes are so registered.

ARTICLE X

SUPPLEMENTAL INDENTURES

This Twenty-Sixth Supplemental Indenture is a supplement to the Original Indenture. As
supplemented by this Twenty-Sixth Supplemental Indenture, the Original Indenture is in all respects
ratified, approved and confirmed, and the Original Indenture and this Twenty-Sixth Supplemental
Indenture shall together constitute one and the same instrument.

ARTICLE XI

INAPPLICABLE PROVISIONS OF THE ORIGINAL INDENTURE

The 2018 Notes shall not constitute Subordinated Securities and the provisions of Article
Twelve of the Original Indenture shall not apply to the Notes.

TESTIMONIUM

This Twenty-Sixth Supplemental Indenture may be executed in any number of counterparts, each
of which so executed shall be deemed to be an original, but all such counterparts shall together
constitute but one and the same instrument.

1

IN WITNESS WHEREOF, the parties hereto have caused this Twenty-Sixth Supplemental Indenture to
be duly executed and their respective corporate seals to be hereunto affixed and attested, all as
of the day and year first written above.

CMS ENERGY CORPORATION

By: /s/ Laura L. Mountcastle

Laura L. Mountcastle

Vice President and Treasurer

Attest:  /s/ Shelley J. Ruckman

THE BANK OF NEW YORK MELLON,

as Trustee

/s/ Laurence J. O  ́Brien

Laurence J. O  ́Brien

Vice President    

Attest: /s/ Timothy W. Casey

2EX-10.1

CONEXANT SYSTEMS, INC.

2011 MANAGEMENT INCENTIVE PLAN

Section 1. Overview. The Management Incentive Plan (the “Plan”) may pay cash bonuses (each, a
“Bonus Award”) to select employees. Bonus Awards are earned and paid semi-annually. The amount of
a Bonus Award is based upon an employee’s Eligible Earnings (as defined in Section 5(a) below),
Bonus Target, performance during the Performance Period, and the Incentive Pool made available for
payments under the Plan for the applicable Performance Period.

Section 2. Purpose. The Plan is designed to focus the efforts of certain employees of Conexant
Systems, Inc. and its subsidiaries (the “Company”) on the continued improvement in the performance
of the Company, and to aid in attracting, motivating and retaining superior employees by providing
an incentive and reward for those employees contributing to the performance of the Company.

Section 3. Performance Year. The Plan is effective for the fiscal 2011 year beginning October 2,
2010 and ending September 30, 2011 (the “Performance Year”) and equally divided into 2 (two)
Performance Halves.

Section 4. Eligibility. Those employees who are determined to be eligible to receive a Bonus Award
are called “Participants.”

(a) Eligible Participants. Except as specifically provided otherwise in this Plan, a
person must be employed by the Company, on active status on the Company payroll or on a
formal leave of absence on the last day of the Performance Period (except as provided in
cases of death or disability as defined in Sections 6 or 7 below) to be eligible for
participation in the Plan. A Participant may work either full-time or part-time as an
employee, as long as other eligibility criteria are met (interns and summer hires are
excluded). Employees who are covered for the full period of the fiscal year by the Sales
Incentive Plan, employees eligible for the Employee Incentive Plan and employees that are
subject to a separate bonus plan (such as for a specific geographic location, line of
business, or other individually-based plans) shall not be eligible to participate in the
Plan.

(b) Determination of Participants. Prior to the beginning of the Performance Year, or as
soon as practicable thereafter, the Compensation Committee shall determine which Named
Executive Officers subject to SEC reporting (“Named Executive Officers”) are Participants,
and the Chairman and Chief Executive Officer shall determine which employees are eligible
to be Participants in the Plan. Additional Participants may be included during the
Performance Year and, as provided herein, an employee’s participation in the Plan may
terminate.

Section 5. Bonus Award. There is no minimum Bonus Award or guaranteed payment. A Participant’s
Bonus Award is calculated with reference to such Participant’s Bonus Target (as defined below),
that Participant’s performance for the Performance Period, and the Incentive Pool (as defined
below) for the Performance Period.

(a) Bonus Targets.

(1) Each Participant has a target (the “Bonus Target”) stated as a
percentage of a Participant’s Eligible Earnings.

(2) Eligible Earnings refers to the Participant’s annual rate of salary at the end of
the Performance Period and shall be calculated as one half of that rate. For
Participants in India, Eligible Earnings refers to the Participant’s annual rate of the
Total Cost-To-Company at the end of the Performance Period, or as deemed appropriate by
the Company, and shall be calculated as one half of that rate. The term “Eligible
Earnings” excludes incentive payments (such as FIRST program awards, sign-on bonuses,
retention bonuses, stock option exercises and vesting of restricted stock and
performance shares), and excludes any payoffs for unused vacation, unused sick time,
earnings from workers’ compensation or any payments while an Employee is on suspension
or disciplinary time-off. What is included in “Eligible Earnings” may be adjusted by
the Company based on local law and payroll practices.

(3) The Compensation Committee establishes individual Bonus Targets for Named Executive
Officers. Bonus Targets for other employees are established by the Company’s Chairman
and Chief Executive Officer in consultation with Human Resources.

(b) Determination of the Incentive Pool Amount. At the end of the Performance Period the
Compensation Committee, in its sole discretion, may identify an amount as the Incentive
Pool, and may take into consideration various metrics when determining whether or not to
identify an amount available for payment of Bonus Awards under the Plan (referred to as the
“Incentive Pool”). The performance metric(s) may be based on, among other things,
achievement of certain financial targets, Company business plans and achievement of certain
goals vs. the Company’s competitors. For fiscal year 2011, the Committee, in its sole
discretion, will determine the size of the Incentive Pool on a semi-annual basis, if any.
The overall pool is capped at 150% of Participants’ target awards, and the Compensation
Committee retains the discretion to go above this cap if it deems appropriate. In
exercising its discretion in determining the size of the Incentive Pool, if any, the
Committee will consider all circumstances existing at the end of each Performance Period
that it deems relevant, including, but not limited to, the achievement of certain fiscal
2011 core operating income goals, market conditions, forecasts and anticipated expenses to
be incurred or payable during fiscal 2011.

(c) Determination of Bonus Award Amount.

(1) A Bonus Award is calculated with reference to: (i) a Participant’s Eligible
Earnings multiplied by that Participant’s Bonus Target (this is called the “Target
Award”), (ii) that Target Award being subject to a pro rata amount based on the
Participant’s length of service in months to the Company during the Performance Period,
(iii) that Participant’s performance for the Performance Period, and (iiii) the
Incentive Pool made available for Bonus Awards under the Plan for the Performance
Period.

(2) The amount of a Bonus Award to a Participant who is a Company Officer is determined
by the Compensation Committee. The amount of a Bonus Award to a Participant who is not
a Named Executive Officer is determined by the executive leader of a Participant’s
business unit or functional group and the Chairman and Chief Executive Officer. A
Participant’s Bonus Award can be either greater than or less than (including zero) a
Participant’s Target Award. The Committee, in its sole discretion, may increase or
decrease individual awards from their target levels, based on individual performance
and available incentive pool.

(3) A Participant’s Bonus Award is linked to an assessment of a Participant’s total job
performance for the Performance Period. Factors that may be considered include but are
not limited to, what a Participant does to advance Conexant’s success and how a
Participant does it, especially leadership, balance of short-term actions with
long-term goals, and resource allocation while prioritizing the needs of customers,
employees and stockholders.

(4) As referenced above, there is neither a minimum nor maximum amount of a Bonus
Award that may be paid to a Participant for the Performance Period. At Conexant’s
discretion, a Bonus Award amount may be prorated for those Participants who are
eligible to participate in the Plan for less than the full Performance Period;
provided, however, all decisions relating to Bonus Awards for Named Executive Officers
must be made by the Compensation Committee.

(d) Payment of Awards. To be eligible to receive a Bonus Award, a Participant must be an
employee in good standing and, on active status or be on a formal leave of absence at the
time the Bonus Awards are distributed. As soon as administratively practicable following
the determination of a Participant’s Bonus Award, but not later than 2.5 months after the
end of the period in which such determination is made, such Bonus Award, less any legally
required withholding, shall be paid to a Participant (unless a Participant is on a formal
leave of absence) or, in the event of a Participant’s death, in accordance with Company
policy as stated in Section 6 hereof. If, at the time a Bonus Award is to be paid, a
Participant is on a formal leave of absence, a Participant shall receive his or her Bonus
Award if and when a Participant returns to active status.

Section 6. Death of a Participant.

(a) Beneficiary. A Participant’s beneficiaries are those specified at the time of a
Participant’s death in a Participant’s will or a Participant’s heirs if a Participant does
not have a valid will. If a Participant dies prior to the date of any payment in question,
the amount otherwise payable shall be paid to a Participant’s beneficiary.

(b) Death during Performance Period. In case of a Participant’s death during the
Performance Period, the Company may pay a pro rata portion of the Bonus Award to which a
Participant would have been entitled for the Performance Period. Such pro rata portion
shall be equal to (i) the ratio which a Participant’s completed calendar months of
employment during the Performance Period bears to 6 multiplied by (ii) the amount to which
the Company determines a Participant would have been entitled, as determined in Section 5
herein, had a Participant continued in Active Status through the end of the Performance
Period.

(c) Death after Performance Period. In case of the death of a Participant after the end of
the Performance Period, but before the delivery of a Bonus Award to which he or she may be
entitled, such Bonus Award shall be delivered to a Participant’s beneficiary.

Section 7. Disability of Participant. In the event of a Participant’s Disability during the
Performance Period, a Participant shall become eligible for a portion of an Award, based on a pro
rata portion of the Performance Period represented by the time prior to the absence from work
caused by the Disability. Disability is the permanent and total disability of a person within the
meaning of Section 22(e)(3) of the Internal Revenue Code of 1986, as amended.

Section 8. Termination of Employment. Upon an employee’s termination during the Performance Period
for any reason other than those specified in Sections 6 or 7 hereof, such former employee shall no
longer be a Participant and shall not have any right to a Bonus Award under the Plan.

Section 9. Miscellaneous

(a) Administration of the Plan. Except as otherwise required for the Named Executive
Officers under the Charter of the Compensation Committee, the Company’s Chairman and Chief
Executive Officer has the sole discretion to: (i) adopt such rules, regulations,
agreements and instruments as it deems necessary to administer the Plan; (ii) interpret the
terms of the Plan; (iii) determine an employee’s eligibility under the Plan; (iv) determine
whether a Participant is to receive a Bonus Award under the Plan; (v) determine the amount
of any Bonus Award to a Participant; (vi) determine when a Bonus Award is to be paid to a
Participant; (vii) amend, suspend or terminate the Plan, without notice; and (viii) take
any and all other actions it deems necessary or advisable for the proper administration of
the Plan.

(b) Notification. A copy of this Plan shall be provided to each Participant upon request.
A Participant shall have no right to or interest in an Award unless and until a
Participant’s Award has been determined and paid to a Participant.

(c) Nature of the Plan. Whether to grant any Bonus Awards under this Plan, and in what
amounts, are under the Compensation Committee’s and management’s discretion. Participation
in this Plan is not intended, nor should it be interpreted, to create any entitlement to
participate in this or any future incentive plans or to receive the same or similar
incentive payments that may be received under this Plan. No Participant should make any
decision based on any hope or expectation of receiving any incentive under this Plan.
Nothing contained in nor will any action under the Plan confer upon any individual any
right to continue in the employment of the Company and does not constitute any contract or
agreement of employment or interfere in any way with the right of the Company to terminate
any individual’s employment.

(d) Termination and Notification. The Company may at any time modify, terminate or from
time to time, suspend and, if suspended, may reinstate the provisions of this Plan.

(e) Withholding Tax. As required by law, federal, state or local taxes that are subject to
the withholding of tax at the source shall be withheld by the Company as necessary to
satisfy such requirements.

(f) Award Limitations. Bonus Awards made under this Plan are not considered for the
purpose of calculating any extra benefits; any termination, severance, redundancy, or
end-of-service premium payments; other bonuses or long-service awards; overtime premiums;
pension or retirement benefits; or future base pay or any other payment to be made by the
Company to a Participant or former Participant.

(g) All Rights Reserved. The Company expressly reserves all rights and control over the
Plan. Although the Company expects that the Plan will continue, the Company may change,
amend, or terminate any provisions of the Plan, or the Plan itself, at any time, in its
sole discretion.

(h) Unfunded Plan. Nothing contained in this plan will be deemed to require the Company to
deposit, invest or set aside amounts for the payment of any Bonus Awards. Participation in
the Plan does not give a Participant any ownership, security, or other rights in any assets
of the Company.

(i) Applicable Law. The Plan will be governed by and construed in accordance with the laws
of the State of Delaware.

(j) Validity. In the event any provision of the Plan is held invalid, void, or
unenforceable, the same will not affect, in any respect whatsoever, the validity of any
other provision of the Plan.

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