NOTICEALLOCATION OF TAX BASIS IN
PRE-RESTRUCTURING CBOT MEMBERSHIPSAMONG CLASS A COMMON STOCK, CLASS B MEMBERSHIPS AND
CBOE EXERCISE RIGHT PRIVILEGESAccording to two private letter rulings from the IRS, and an opinion of counsel received
in connection with the 2005 restructuring transactions, you recognized no gain or loss withrespect to the receipt of shares of Class A common stock of CBOT Holdings, a Class B
membership in the CBOT exchange subsidiary or a CBOE exercise right privilege (for Series B-1(Full) members) in connection with the restructuring transactions. Your aggregate tax basis in theCBOT membership you held prior to the restructuring transactions is the same as your aggregatetax basis in the Class A common stock, the Class B membership and the CBOE exercise rightprivilege (for Series B-1 (Full) members) you received in the restructuring transactions.
If you sell some but not all of the interests you received in connection with therestructuring transactions (for example, if you sell your shares of Class A common stock of
CBOT Holdings but not your Class B membership in the CBOT subsidiary), you will need toallocate some or all of your tax basis in the pre-restructuring CBOT membership to the interests
you sell.
As a general matter, your tax basis in the Class A common stock and Class B
membership (without the CBOE exercise right privilege) should be equal to what you paid for theCBOT equity and trading right component, respectively, of the CBOT membership held prior tothe restructuring transactions. In addition, if you are a Series B-1 (Full) member, your tax basis
in the CBOE exercise right privilege should be equal to what you paid for the CBOE exercise
right privilege component of your pre-restructuring CBOT Full Membership.
Practically speaking, however, it is unlikely that you allocated the purchase price for yourpre-restructuring CBOT membership among its components or had any information on thevaluation of the components at the time you acquired your pre-restructuring CBOT membership.
If this is the case, you will need to make a reasonable determination of how much you paid foreach component, or, in other words, how to allocate the total amount you paid or your total tax
basis in your pre-restructuring CBOT membership (the “Total Tax Basis”) among the various
components that made up your pre-restructuring CBOT membership.
Although there may be other appropriate methodologies, one possible approach would be
to allocate your Total Tax Basis among the component interests based on relative values of thecomponent interests as of the date or dates objective information regarding such values became
available. Three examples of such allocations are presented below based on market assumptions
as of various key dates.
For more information regarding the information in this Notice, please contact Glen M.
Johnson, Senior Vice President and Chief Financial Officer, at (312) 435-3457.

Example 1: The following allocates a Full Member’s Total Tax Basis among the Class A
common stock, the Series B-1 (Full) membership and the CBOE exercise right privilege based onmarket information we have in our records on or about May 3, 2005, the first date that we have
any trading information for the interests granted to Full Members in connection with therestructuring transactions (27,338 shares of Class A common stock, a Series B-1 (Full)membership and a CBOE exercise right privilege).1
Our records reflect the following trading or sales prices for each component on or about
this date:
One Series B-1 (Full) membership$350,000 2

One CBOE exercise right privilege$100,000 3

27,338 shares of Class A common stock$1,175,000 4Thus, assume someone paid $1,000,000 for a Full Membership in 2003. One approach
would be to allocate the member’s $1,000,000 Total Tax Basis among the component interests asfollows:
RelativeValue

Percentage of the Total
Relative Value

Allocated TaxBasisSeries B-1 (Full)Membership$350,000

21.54%$215,400

CBOE exercise rightprivilege$100,000

6.15%$61,500

27,338 shares of Class A
common stock$1,175,000

72.31%$723,100

Total$1,625,000

100%$1,000,000

1

Our demutualization was effected on April 22, 2005. At that time, a market was established for the Class
A common stock of CBOT Holdings, Class B memberships in the CBOT subsidiary and CBOE exercise
right privileges. The shares of Class A common stock issued in the demutualization were subject torestrictions on transfer and generally could not be transferred apart from the associated Class B
membership prior to April 2006. The first trading of any kind after the demutualization was a bundledtrade of a Series B-1 (Full) membership with the associated Class A common stock and CBOE exercise
right privilege on May 3, 2005 at a price of $1,625,000.
2
We do not have separate pricing information for Series B-1 (Full) memberships as of May 3, 2005. The
closest date information is available is September 20, 2005. On that date, we show a sale price of $350,000
for a Series B-1 (Full) membership.
3
We do not have separate pricing information for CBOE exercise right privileges as of May 3, 2005. The
closest date information is available is May 31, 2005. On that date, we show a sale price of $100,000 for a
CBOE exercise right privilege.
4We do not have separate pricing information for 27,338 shares of Class A common stock as of May 3,2005. However, we can estimate fair market value as follows: $1,625,000 (the price of the May 3, 2005
bundled trade of one Series B-1 (Full) membership with the associated 27,338 shares of Class A common
stock and one CBOE exercise right privilege), less $100,000 (the price of a CBOE exercise right privilege
as of May 31, 2005), less $350,000 (the price of a Series B-1 (Full) membership as of September 20, 2005)= $1,175,000.

2

Example 2: The following allocates a Full Member’s Total Tax Basis among the Class A
common stock, the Series B-1 (Full) membership and the CBOE exercise right privilege based onmarket information we have in our records on or about October 18, 2005, the day before the Class
A common stock began trading on the New York Stock Exchange.
Our records reflect the following trading or sales prices for each component on or about
this date:
One Series B-1 (Full) membership$335,000 5

One CBOE exercise right privilege$95,000 6

27,338 shares of Class A common stock$2,045,000 7

Again, assume someone paid $1,000,000 for a Full Membership in 2003. One approach
would be to allocate the member’s $1,000,000 Total Tax Basis among the component interests
based on their relative value on or about October 18, 2005, as follows:
Relative Value

Percentage of theTotal RelativeValue

Allocated Tax BasisSeries B-1 (Full)
Membership$335,000

13.54%$135,400

CBOE exercise rightprivilege$95,000

3.84%$38,400

27,338 shares of Class Acommon stock$2,045,00082.62%$826,200

Total$2,475,000

100%$1,000,000

5

We do not have separate pricing information for Series B-1 (Full) memberships as of October 18, 2005.
The closest date information is available is October 21, 2005. On that date, we show a sale price of$335,000 for a Series B-1 (Full) membership.
6
We do not have separate pricing information for CBOE exercise right privileges as of October 18, 2005.
The closest date information is available is October 14, 2005. On that date, we show a sale price of$95,000 for a CBOE exercise right privilege.
7We do not have separate pricing information for 27,338 shares of Class A common stock as of October18, 2005. However, we show a bundled trade of a Series B-1 (Full) membership with the associated 27,338
shares of Class A common stock and one CBOE exercise right privilege on October 20, 2005 at a price of$2,475,000. As a result, we can estimate fair market value as follows: $2,475,000 (the price of the October
20, 2005 bundled trade of a Series B-1 (Full) membership with the associated Class A common stock andCBOE exercise right privilege), less $95,000 (the price of a CBOE exercise right privilege on October 14,2005), less $335,000 (the price of a Series B-1 (Full) membership on October 21, 2005) = $2,045,000.

3

Example 3: The following allocates a Full Member’s Total Tax Basis among the Class A
common stock, the Series B-1 (Full) membership and the CBOE exercise right privilege based onmarket information we have in our records on or about October 19, 2005, the date the Class A
common stock began trading on the New York Stock Exchange.
Our records reflect the following trading or sales prices for each component on or about
this date:
One Series B-1 (Full) membership$335,000 8

One CBOE exercise right privilege$95,000 927,338 shares of Class A common stock$2,195,241 10

Again, assume someone paid $1,000,000 for a Full Membership in 2003. One approach
would be to allocate the member’s $1,000,000 Total Tax Basis among the component interests
based on their relative value on or about October 19, 2005, as follows:
Relative Value

Percentage of theTotal RelativeValue

Allocated Tax BasisSeries B-1 (Full)Membership$335,000

12.76%$127,600

CBOE exercise rightprivilege$95,000

3.62%$36,200

27,338 shares of Class
A common stock$2,195,241(27,338 shares x$80.30 per share)

83.62%$836,200

Total$2,625,241100%$1,000,000

This shall not constitute a recommendation to sell all or any of the interests issued to CBOT
members in connection with the CBOT’s 2005 demutualization. The sale of one or more ofsuch interests may have adverse consequences to you. For additional information, please
see the information set forth under the heading “Risk Factors – Additional Risks Relatingto CBOT Members” in CBOT Holdings’ proxy statement filed with the Securities andExchange Commission on March 2, 2007, under the heading “Business – Members” in
CBOT Holdings’ Annual Report on Form 10-K filed with the Securities and Exchange
Commission on March 1, 2007, and in its other filings with the Securities and Exchange
Commission.
8

We do not have separate pricing information for Series B-1 (Full) memberships as of October 19, 2005.
The closest date information is available is October 21, 2005. On that date, we show a sale price of$335,000 for a Series B-1 (Full) membership.
9We do not have separate pricing information for CBOE exercise right privileges as of October 19, 2005.
The closest date information is available is October 14, 2005. On that date, we show a sale price of$95,000 for a CBOE exercise right privilege.
10Based $80.30 per share, which was the closing price of the Class A common stock on the New York
Stock Exchange on October 19, 2005.

4

This is not tax advice to any particular member, and does not purport to cover all issues for
all members, or for the CBOT. This discussion is not an opinion that can be used for thepurpose of avoiding penalties that may be imposed under the Internal Revenue Code.
Rather, this is a limited set of observations about how the federal income tax law applies tothe circumstances of the CBOT restructuring, how the IRS views the restructuring in
general, and several issues that members may have to consider. The tax considerations may
be materially different for certain members, including in particular any member who does
not hold the CBOT membership as a capital asset, and any member who acquired theCBOT membership other than by purchase. In all events, however, we strongly recommendthat each member consult his or her tax advisor concerning the federal income tax
consequences of the restructuring and of any sale or exchange of interests following therestructuring, as well as state, local and foreign tax consequences.
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