<PAGE>   1
                       SECURITIES AND EXCHANGE COMMISSION

                             WASHINGTON, D.C. 20549

                                    FORM 10-Q


/X/   QUARTERLY REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES
      EXCHANGE ACT OF 1934 FOR THE QUARTERLY PERIOD ENDED SEPTEMBER 30, 1996

                                       OR

/ /   TRANSITION REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES
      EXCHANGE ACT OF 1934 FOR THE TRANSITION PERIOD FROM          TO


                         Commission file number 0-21518

                            IEA INCOME FUND XII, L.P.
             (Exact name of registrant as specified in its charter)


          California                                           94-3143940
(State or other jurisdiction of                             (I.R.S. Employer
incorporation or organization)                              Identification No.)

         444 Market Street, 15th Floor, San Francisco, California 94111
               (Address of principal executive offices) (Zip Code)

                                 (415) 677-8990
              (Registrant's telephone number, including area code)


Indicate by check mark whether the registrant (1) has filed all reports required
to be filed by Section 13 or 15(d) of the Securities Exchange Act of 1934 during
the preceding 12 months (or for such shorter period that the registrant was
required to file such reports), and (2) has been subject to such filing
requirements for the past 90 days.   Yes  X .  No    .
                                         ---      ---
<PAGE>   2
                            IEA INCOME FUND XII, L.P.

                      REPORT ON FORM 10-Q FOR THE QUARTERLY
                         PERIOD ENDED SEPTEMBER 30, 1996

                                TABLE OF CONTENTS

<TABLE>
<CAPTION>

                                                                                                                   PAGE
PART I - FINANCIAL INFORMATION

<S>                                                                                                                <C>
Item 1    Financial Statements

          Balance Sheets - September 30, 1996 (unaudited) and December 31, 1995                                     4

          Statements of Operations for the three and nine months ended September 30, 1996 and 1995 (unaudited)      5

          Statements of Cash Flows for the nine months ended September 30, 1996 and 1995 (unaudited)                6

          Notes to Financial Statements (unaudited)                                                                 7

Item 2    Management's Discussion and Analysis of Financial Condition and Results of Operations                    10


PART II - OTHER INFORMATION

Item 5    Other Materially Important Events                                                                        12

Item 6    Exhibit and Reports on Form 8-K                                                                          12
</TABLE>





                                        2
<PAGE>   3
                         PART I - FINANCIAL INFORMATION


Item 1.   Financial Statements

          Presented herein are the Registrant's balance sheets as of September
          30, 1996 and December 31, 1995, statements of operations for the three
          and nine months ended September 30, 1996 and 1995, and statements of
          cash flows for the nine months ended September 30, 1996 and 1995.




                                        3
<PAGE>   4
                            IEA INCOME FUND XII, L.P.

                                 BALANCE SHEETS

                                   (UNAUDITED)

<TABLE>
<CAPTION>

                                                                                September 30,        December 31,
                                                                                    1996                1995
                                                                                -------------        ------------
<S>                                                                             <C>                  <C>
                   Assets

Current assets:
     Cash, includes $492,808 at September 30, 1996 and $459,603
         at December 31, 1995 in interest-bearing accounts                      $   493,229              459,786
     Short-term investments                                                       1,838,400            2,367,716
     Net lease receivables due from Leasing Company
         (notes 1 and 2)                                                          1,152,907            1,300,391
                                                                                -----------           ----------

              Total current assets                                                3,484,536            4,127,893
                                                                                -----------           ----------

Container rental equipment, at cost                                              63,202,036           63,426,137
     Less accumulated depreciation                                               15,058,876           12,361,962
                                                                                -----------           ----------
         Net container rental equipment                                          48,143,160           51,064,175
                                                                                -----------           ----------

Organizational costs, net                                                           205,896              386,749
                                                                                -----------          -----------

                                                                                $51,833,592          $55,578,817
                                                                                ===========          ===========
     Liabilities and Partners' Capital

Current liabilities:
     Accrued expenses                                                           $   453,246          $   430,500
     Due to general partner (notes 1 and 3)                                         338,382              889,475
     Due to manufacturer                                                                 --              221,850
                                                                                -----------          -----------

              Total current liabilities                                             791,628            1,541,825
                                                                                -----------          -----------
Partners' capital (deficit):
     General partner                                                                (31,888)             (58,767)
     Limited partners                                                            51,073,852           54,095,759
                                                                                -----------          -----------

              Total partners' capital                                            51,041,964           54,036,992
                                                                                -----------          -----------

                                                                                $51,833,592          $55,578,817
                                                                                ===========          ===========
</TABLE>


        The accompanying notes are an integral part of these statements.

                                        4
<PAGE>   5
                            IEA INCOME FUND XII, L.P.

                            STATEMENTS OF OPERATIONS

                                   (UNAUDITED)

<TABLE>
<CAPTION>

                                                            Three Months Ended                Nine Months Ended
                                                     -------------------------------    ------------------------------
                                                     September 30,     September 30,    September 30,    September 30,
                                                          1996             1995             1996             1995
                                                     ------------     --------------    -------------    -------------
<S>                                                  <C>              <C>               <C>              <C>
Net lease revenue (notes 1 and 4)                    $1,674,886         $2,249,891        $5,297,219       $6,599,072
Other operating expenses:
   Depreciation and amortization                        982,278          1,382,410         2,949,465        3,350,393
   Other general and administrative expenses             26,974             11,864            75,166           82,698
                                                     ----------         ----------        ----------       ----------
                                                      1,009,252          1,394,274         3,024,631        3,433,091
                                                     ----------         ----------        ----------       ----------
     Earnings from operations                           665,634            855,617         2,272,588        3,165,981
Other income:
   Interest income                                       33,503             34,582            99,477          107,577
   Net gain on disposal of equipment                     23,421             32,049            57,403           44,792
                                                     ----------         ----------        ----------       ----------
                                                         56,924             66,631           156,880          152,369
                                                     ----------         ----------        ----------       ----------
     Net earnings                                    $  722,558         $  922,248        $2,429,468       $3,318,350
                                                     ==========         ==========        ==========       ==========
Allocation of net earnings:
   General partner                                   $   99,452         $  114,922        $  298,104       $  299,439
   Limited partners                                     623,106            807,326         2,131,364        3,018,911
                                                     ----------         ----------        ----------       ----------
                                                     $  722,558         $  922,248        $2,429,468       $3,318,350
                                                     ==========         ==========        ==========       ==========
Limited partners' per unit share of net earnings     $      .18         $      .23        $      .61       $      .86
                                                     ==========         ==========        ==========       ==========
</TABLE>

        The accompanying notes are an integral part of these statements.

                                        5
<PAGE>   6
                            IEA INCOME FUND XII, L.P.

                            STATEMENTS OF CASH FLOWS

                                   (UNAUDITED)


<TABLE>
<CAPTION>
                                                                Nine Months Ended
                                                          ------------------------------
                                                          September 30,    September 30,
                                                              1996             1995
                                                          -------------    -------------
<S>                                                       <C>              <C>
Net cash provided by operating activities                  $ 5,438,544      $ 6,718,473

Cash flows provided by (used in) investing activities:
   Proceeds from sale of container rental equipment            351,726          246,338
   Purchase of container rental equipment                     (306,330)         (59,771)
   Acquisition fees paid to general partner                   (555,317)        (722,000)
                                                           -----------      -----------

         Net cash used in investing activities                (509,921)        (535,433)
                                                           -----------      -----------

Cash flows used in financing activities:
   Distribution to partners                                 (5,424,496)      (5,547,780)
                                                           -----------      -----------

Net increase (decrease) in cash and cash equivalents          (495,873)         635,260

Cash and cash equivalents at January 1                       2,827,502        2,160,789
                                                           -----------      -----------

Cash and cash equivalents at September 30                  $ 2,331,629      $ 2,796,049
                                                           ===========      ===========
</TABLE>



        The accompanying notes are an integral part of these statements.

                                       6
<PAGE>   7
                            IEA INCOME FUND XII, L.P.

                     NOTES TO UNAUDITED FINANCIAL STATEMENTS


(1)   Summary of Significant Accounting Policies

      (a) Nature of Operations

          IEA Income Fund XII, L.P. (the "Partnership") is a limited partnership
          organized under the laws of the State of California on August 28, 1991
          for the purpose of owning and leasing marine cargo containers. Cronos
          Capital Corp. ("CCC") is the general partner and, with its affiliate
          Cronos Containers Limited (the "Leasing Company"), manages and
          controls the business of the Partnership.

      (b) Leasing Company and Leasing Agent Agreement

          The Partnership has entered into a Leasing Agent Agreement whereby the
          Leasing Company has the responsibility to manage the leasing
          operations of all equipment owned by the Partnership. Pursuant to the
          Agreement, the Leasing Company is responsible for leasing, managing
          and re-leasing the Partnership's containers to ocean carriers and has
          full discretion over which ocean carriers and suppliers of goods and
          services it may deal with. The Leasing Agent Agreement permits the
          Leasing Company to use the containers owned by the Partnership,
          together with other containers owned or managed by the Leasing Company
          and its affiliates, as part of a single fleet operated without regard
          to ownership. Since the Leasing Agent Agreement meets the definition
          of an operating lease in Statement of Financial Accounting Standards
          (SFAS) No. 13, it is accounted for as a lease under which the
          Partnership is lessor and the Leasing Company is lessee.

          The Leasing Agent Agreement generally provides that the Leasing
          Company will make payments to the Partnership based upon rentals
          collected from ocean carriers after deducting direct operating
          expenses and management fees to CCC and the Leasing Company. The
          Leasing Company leases containers to ocean carriers, generally under
          operating leases which are either master leases or term leases (mostly
          two to five years). Master leases do not specify the exact number of
          containers to be leased or the term that each container will remain on
          hire but allow the ocean carrier to pick up and drop off containers at
          various locations; rentals are based upon the number of containers
          used and the applicable per-diem rate. Accordingly, rentals under
          master leases are all variable and contingent upon the number of
          containers used. Most containers are leased to ocean carriers under
          master leases; leasing agreements with fixed payment terms are not
          material to the financial statements. Since there are no material
          minimum lease rentals, no disclosure of minimum lease rentals is
          provided in these financial statements.

      (c) Basis of Accounting

          The Partnership utilizes the accrual method of accounting. Revenue is
          recognized when earned.

          The Partnership has determined that for accounting purposes the
          Leasing Agent Agreement is a lease, and the receivables, payables,
          gross revenues and operating expenses attributable to the containers
          managed by the Leasing Company are, for accounting purposes, those of
          the Leasing Company and not of the Partnership. Consequently, the
          Partnership's balance sheets and statements of operations display the
          payments to be received by the Partnership from the Leasing Company as
          the Partnership's receivables and revenues.




                                                                     (Continued)



                                       7
<PAGE>   8
                          IEA INCOME FUND XII, L.P.

                   NOTES TO UNAUDITED FINANCIAL STATEMENTS


      (d) Financial Statement Presentation

          These financial statements have been prepared without audit. Certain
          information and footnote disclosures normally included in financial
          statements prepared in accordance with generally accepted accounting
          procedures have been omitted. It is suggested that these financial
          statements be read in conjunction with the financial statements and
          accompanying notes in the Partnership's latest annual report on Form
          10-K.

          The preparation of financial statements in conformity with generally
          accepted accounting principles (GAAP) requires the Partnership to make
          estimates and assumptions that affect the reported amounts of assets
          and liabilities and disclosure of contingent assets and liabilities at
          the date of the financial statements and the reported amounts of
          revenues and expenses during the reported period.

          The interim financial statements presented herewith reflect all
          adjustments of a normal recurring nature which are, in the opinion of
          management, necessary to a fair statement of the financial condition
          and results of operations for the interim periods presented.

(2)   Net Lease Receivables Due from Leasing Company

      Net lease receivables due from the Leasing Company are determined by
      deducting direct operating payables and accrued expenses, base management
      fees payable, and reimbursed administrative expenses payable to CCC, the
      Leasing Company, and its affiliates from the rental billings payable by
      the Leasing Company to the Partnership under operating leases to ocean
      carriers for the containers owned by the Partnership. Net lease
      receivables at September 30, 1996 and December 31, 1995 were as follows:

<TABLE>
<CAPTION>
                                                                 September 30,       December 31,
                                                                     1996               1995
                                                                 -------------       ------------
<S>                                                              <C>                 <C>
      Lease receivables, net of doubtful accounts
          of $333,771 at September 30, 1996 and $343,373 at
          December 31, 1995                                       $2,344,091          $2,675,630
      Less:
      Direct operating payables and accrued expenses                 680,742             746,823
      Damage protection reserve                                      185,018             241,172
      Base management fees                                           278,540             334,219
      Reimbursed administrative expenses                              46,884              53,025
                                                                  ----------          ----------
                                                                  $1,152,907          $1,300,391
                                                                  ==========          ==========
</TABLE>


(3)   Due to General Partner

      The amounts due to CCC at September 30, 1996 and December 31, 1995 consist
      of acquisition fees.


                                                                     (Continued)



                                       8
<PAGE>   9
                            IEA INCOME FUND XII, L.P.

                     NOTES TO UNAUDITED FINANCIAL STATEMENTS


(4)   Net Lease Revenue

      Net lease revenue is determined by deducting direct operating expenses,
management fees and reimbursed administrative expenses to CCC, the Leasing
Company, and its affiliates from the rental revenue billed by the Leasing
Company under operating leases to ocean carriers for the containers owned by the
Partnership. Net lease revenue for the three and nine-month periods ended
September 30, 1996 and 1995 was as follows:

<TABLE>
<CAPTION>
                                            Three Months Ended              Nine Months Ended
                                       ----------------------------  ----------------------------
                                       September 30,  September 30,  September 30,  September 30,
                                           1996           1995           1996           1995
                                       -------------  -------------  -------------  -------------
<S>                                    <C>            <C>            <C>            <C>
Rental revenue                          $2,656,463     $3,138,632     $8,199,612     $9,200,276
Rental equipment operating expenses        653,221        486,440      1,895,608      1,454,049
Base management fees                       179,780        212,659        558,407        629,980
Reimbursed administrative expenses         148,576        189,642        448,378        517,175
                                        ----------     ----------     ----------     ----------
                                        $1,674,886     $2,249,891     $5,297,219     $6,599,072
                                        ==========     ==========     ==========     ==========

</TABLE>



                                       9
<PAGE>   10
Item 2.  Management's Discussion and Analysis of Financial Condition and Results
         of Operations

It is suggested that the following discussion be read in conjunction with the
Registrant's most recent annual report on Form 10-K.

1)    Material changes in financial condition between September 30, 1996 and
      December 31, 1995.

      At September 30, 1996, the Registrant had $2,331,629 in cash and cash
      equivalents, a decrease of $495,873 from the December 31, 1995 cash
      balances. During the first nine months of 1996, the Registrant expended
      $306,330 of cash generated from sales proceeds to pay for additional dry
      cargo containers. At September 30, 1996, the Registrant committed to
      purchase an additional 68 twenty-foot, 23 forty-foot, and 22 forty-foot
      high-cube dry cargo containers, replacing containers which have been lost
      or damaged beyond repair, at an aggregate manufacturer's invoice cost of
      $323,975. Approximately $324,000 in cash generated from equipment sales,
      reserved as part of the Registrant's September 30, 1996 cash balances,
      will be used to finance these purchases. Throughout the remainder of 1996,
      the Registrant may use cash generated from equipment sales to purchase and
      replace containers which have been lost or damaged beyond repair. Amounts
      not used to purchase and replace containers may be distributed to its
      partners.

      Net lease receivables at September 30, 1996 declined when compared to
      December 31, 1995. Contributing to this decline were favorable collections
      of the Registrant's lease receivables and the Registrant's declining
      operating results during the first nine months of 1996. The Registrant's
      cash distribution from operations for the third quarter of 1996, payable
      in the fourth quarter of 1996, was 9% (annualized) of the limited
      partners' original capital contribution, consistent with the 1996 second
      quarter distribution.

      The statements contained in the following discussion are based on current
      expectations. These statements are forward looking and actual results may
      differ materially. Indicative of the cyclical nature of the container
      leasing business, containerized trade slowed in the last quarter of 1995,
      and excess inventories began to develop. This slowdown has resulted in
      reduced equipment utilization and lower per-diem rental rates in the
      container leasing industry during the first nine months of 1996.
      Accordingly, the Registrant's average dry cargo container utilization rate
      declined from 85% at December 31, 1995, to 83% at September 30, 1996. The
      refrigerated container utilization rate declined from 93% at December 31,
      1995, to 89% at September 30, 1996. During the first nine months of 1996,
      the Leasing Company implemented various marketing strategies, including
      but not limited to, offering incentives to shipping companies and
      repositioning containers to high demand locations in order to counter the
      market conditions. Ancillary revenues have fallen, and free-day incentives
      offered to the shipping lines have increased. In addition, rental
      equipment operating expenses of the Registrant have increased due to
      higher storage and handling costs associated with the off-hire fleet, and
      increased repositioning costs. These leasing market conditions are
      expected to adversely impact the Registrant's results from operations
      through the remainder of 1996 and into 1997.


2)    Material changes in the results of operations between the three and
      nine-month periods ended September 30, 1996 and the three and nine-month
      periods ended September 30, 1995.

      Net lease revenue for the three and nine-month periods ended September 30,
      1996 was $1,674,886 and $5,297,219, respectively, a decline of
      approximately 26% and 20% from the same periods in the prior year,
      respectively. Gross rental revenue (a component of net lease revenue) for
      the three and nine-month periods ended September 30, 1996 was $2,656,463
      and $8,199,612, respectively, a decline of 15% and 11% from the same
      periods in the prior year, respectively. During 1996, gross rental revenue
      was primarily impacted by the Registrant's lower per-diem rental rates and
      utilization levels for both the dry cargo and refrigerated container
      fleets. Average dry cargo container per-diem rental rates declined
      approximately 6% and 3%, when compared to the three and nine-month periods
      ended September 30, 1996, respectively, when compared to the same periods
      in the prior year. Average refrigerated container per-diem rental rates
      declined approximately 2% in each of the three and nine-month periods
      ended September 30, 1996, respectively, when compared to the same periods
      in the prior year.


                                       10
<PAGE>   11
The Registrant's average fleet size and utilization rates for the three and
nine-month periods ended September 30, 1996 and 1995 were as follows:


<TABLE>
<CAPTION>
                                              Three Months Ended              Nine Months Ended
                                          ----------------------------   -----------------------------
                                          September 30,  September 30,   September 30,    September 30,
                                              1996           1995             1996            1995
                                          -------------  -------------   -------------    ------------
<S>                                       <C>            <C>             <C>              <C>
Average Fleet Size (measured in
  twenty-foot equivalent units (TEU))
    Dry cargo containers                      20,295         20,340        20,299         20,379
    Refrigerated containers                      811            815           812            815
Average Utilization
    Dry cargo containers                          82%            89%           83%            90%
    Refrigerated containers                       88%            95%           89%            98%
</TABLE>

Rental equipment operating expenses were 25% and 23% of the Registrant's gross
lease revenue during the three and nine-month periods ended September 30, 1996,
respectively, as compared to 15% and 16% during the three and nine-month periods
ended September 30, 1995, respectively. These increases were largely
attributable to a decline in gross lease revenue resulting from lower
utilization rates, lower per-diem rates, a downward trend in ancillary revenue,
and an increase in free-day incentives offered to shipping companies. Costs
associated with lower utilization levels, including handling, storage and
repositioning also contributed to the increase in the rental equipment operating
expenses, as a percentage of gross lease revenue. The Registrant's operating
performance contributed to the decline in base management fees, when compared to
the same periods in the prior year.



                                       11
<PAGE>   12
                           PART II - OTHER INFORMATION


Item 5.   Other Materially Important Events

          Equipment Acquisitions

          During the three-month period ended September 30, 1996, the Registrant
          purchased 22 forty-foot dry cargo containers at an average cost of
          $3,840 per container.


Item 6.   Exhibits and Reports on Form 8-K

(a)   Exhibits

<TABLE>
<CAPTION>
Exhibit
   No.                            Description                                         Method of Filing
-------                           -----------                                         ----------------
<S>         <C>                                                                       <C>
   3(a)     Limited Partnership Agreement of the Registrant, amended and              *
            restated as of December 2, 1991

   3(b)     Certificate of Limited Partnership of the Registrant                      **

   10       Form of Leasing Agent Agreement with Cronos Containers Limited            ***

   27       Financial Data Schedule                                                   Filed with this document
</TABLE>



(b)   Report on Form 8-K

      In lieu of filing a current report on Form 8-K, the Registrant has
      provided in Part II, Item 5 hereof, a description of its purchase of
      marine cargo containers during the three-month period ended September 30,
      1996.





-----------------


*      Incorporated by reference to Exhibit "A" to the Prospectus of the
       Registrant dated December 2, 1991, included as part of Registration
       Statement on Form S-1 (No. 33-42697)

**     Incorporated by reference to Exhibit 3.2 to the Registration Statement on
       Form S-1 (No. 33-42697)

***    Incorporated by reference to Exhibit 10.2 to the Registration Statement
       on Form S-1 (No. 33-42697)



                                       12
<PAGE>   13
                                   SIGNATURES


         Pursuant to the requirements of the Securities Exchange Act of 1934,
the Registrant has duly caused this Report to be signed on its behalf by the
undersigned thereunto duly authorized.



                                   IEA INCOME FUND XII, L.P.

                                   By  Cronos Capital Corp.
                                       The General Partner



                                   By  /s/ JOHN KALLAS
                                       ----------------------------------------
                                       John Kallas
                                       Vice President, Treasurer
                                       Principal Financial & Accounting Officer



Date:  November 11, 1996




                                       13
<PAGE>   14
                                  EXHIBIT INDEX


<TABLE>
<CAPTION>

Exhibit
  No.                                  Description                                     Method of Filing
-------                                -----------                                     ----------------
<S>            <C>                                                                     <C>
   3(a)        Limited Partnership Agreement of the Registrant, amended and            *
               restated as of December 2, 1991

   3(b)        Certificate of Limited Partnership of the Registrant                    **

   10          Form of Leasing Agent Agreement with Cronos Containers Limited          ***

   27          Financial Data Schedule                                                 Filed with this document
</TABLE>







--------------

*      Incorporated by reference to Exhibit "A" to the Prospectus of the
       Registrant dated December 2, 1991, included as part of Registration
       Statement on Form S-1 (No. 33-42697)

**     Incorporated by reference to Exhibit 3.2 to the Registration Statement on
       Form S-1 (No. 33-42697)

***    Incorporated by reference to Exhibit 10.2 to the Registration Statement
       on Form S-1 (No. 33-42697)