<PAGE>   1
 
================================================================================
 
                                 UNITED STATES
 
                       SECURITIES AND EXCHANGE COMMISSION
                             WASHINGTON, D.C. 20549
 
                                   FORM 10-K
 
(MARK ONE)
[X]   ANNUAL REPORT PURSUANT TO SECTION 13 OR 15(D) OF THE
                SECURITIES EXCHANGE ACT OF 1934 [FEE REQUIRED]
 
                  FOR THE FISCAL YEAR ENDED DECEMBER 31, 1997
 
                                       OR
 
[  ]   TRANSITION REPORT PURSUANT TO SECTION 13 OR 15(D) OF THE
                 SECURITIES EXCHANGE ACT OF 1934 [NO FEE REQUIRED]
 
        FOR THE TRANSITION PERIOD FROM ______________ TO ______________
 
                          COMMISSION FILE NO. 33-13437
 
                         DEL TACO INCOME PROPERTIES IV
                       (A CALIFORNIA LIMITED PARTNERSHIP)
             (EXACT NAME OF REGISTRANT AS SPECIFIED IN ITS CHARTER)
 
                                   CALIFORNIA
                        (STATE OR OTHER JURISDICTION OF
                         INCORPORATION OR ORGANIZATION)
 
                          23041 AVENIDA DE LA CARLOTA
                            LAGUNA HILLS, CALIFORNIA
                    (ADDRESS OF PRINCIPAL EXECUTIVE OFFICES)
 
                                   33-0241855
                                (I.R.S. EMPLOYER
                             IDENTIFICATION NUMBER)
 
                                     92653
                                   (ZIP CODE)
 
       REGISTRANT'S TELEPHONE NUMBER, INCLUDING AREA CODE: (714) 462-9300
 
        SECURITIES REGISTERED PURSUANT TO SECTION 12(B) OF THE ACT: NONE
 
        SECURITIES REGISTERED PURSUANT TO SECTION 12(G) OF THE ACT: NONE
 
     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 ___
 
                      DOCUMENTS INCORPORATED BY REFERENCE
 
     Portions of the registrant's Form S-11 Registration Statement filed June 5,
1987 are incorporated by reference into Part IV of this report.
 
================================================================================
<PAGE>   2
                                     PART I

ITEM 1. BUSINESS

The Registrant is a publicly-held Limited Partnership organized under the
California Uniform Limited Partnership Act. In accordance with the Partnership
Agreement, the Registrant's General Partner is Del Taco, Inc., a California
corporation ("General Partner"). The Registrant sold 165,415 Units aggregating
$4,135,375 through an offering of Limited Partnership Units from June 5, 1987
through June 3, 1988.

The Registrant has engaged in the business of acquiring sites in California for
the construction of three Mexican-American restaurants for long-term lease to
Del Taco, Inc. for operation under the Del Taco trade name. Each Property is
leased for 32 years on a triple-net basis for a rent equal to twelve percent of
gross sales of the restaurant constructed thereon. The activities of the
Registrant relating to acquisition and development of the Properties is
presented under Item 2 below. The term of the Partnership Agreement is until
December 31, 2027 unless terminated earlier by means provided therein.

Because the three Properties owned by the Registrant constitute virtually all of
the Registrant's income producing assets, the business of the Registrant is
almost entirely dependent on the success of the Del Taco trade name restaurants
which lease those Properties. In turn, the success of those restaurants, which
are not operated by the Registrant, is dependent on a large variety of factors,
including, but not limited to, consumer demand and preference for fast food, in
general, and for Mexican-American food in particular.

The Registrant has no full time employees. The General Partner is vested with
full authority as to the general management and supervision of the business and
affairs of the Registrant, and has a one percent interest in the profits or
losses and distributions of the Registrant. Limited Partners have no right to
participate in the management or conduct of such business and affairs.


                                        2


<PAGE>   3
ITEM 2. PROPERTIES

The Registrant has acquired three Properties with proceeds obtained from the
sale of Limited Partnership Units:


<TABLE>
<CAPTION>
                                                                                      Date of 
                                          Date of              Restaurant            Commencement
Address              City, State          Acquisition          Constructed           of Operation (1)
-------              -----------          -----------          -----------           ----------------
<S>                  <C>                  <C>                  <C>                   <C>
Orangethorpe         Placentia,           August 5, 1988        60 seat with drive    March 27,
Avenue               CA                                         through service       1989
                                                                window

Lakeshore            Lake Elsinore,       February 1, 1989      60 seat with drive    April 18,   (2)
Drive                CA                                         through service       1990
                                                                window

Highland Avenue      San Bernardino,      December 8, 1989      60 seat with drive    July 13,
                     CA                                         through service       1990
                                                                window
</TABLE>


(1)      Commencement of operation is the first date Del Taco, Inc., as lessee,
         operated the facility on the site as a Del Taco restaurant.

(2)      The restaurant is subleased to a franchisee of Del Taco, Inc. and the
         restaurant operates as a Del Taco restaurant.

                                     PART II


ITEM 3. LEGAL PROCEEDINGS

The Registrant is not a party to any material pending legal proceedings.


ITEM 4. SUBMISSIONS OF MATTERS TO A VOTE OF SECURITY HOLDERS

None.

ITEM 5. MARKET FOR THE REGISTRANT'S COMMON EQUITY AND RELATED SECURITY HOLDER
MATTERS

The Registrant, a publicly-held Limited Partnership, sold 165,415 ($4,135,375)
Limited Partnership Units during the offering period ended June 3, 1988 and
currently has 386 Limited Partners of record. There is no public market for the
trading of the Units. Distributions made by the Registrant to the Limited
Partners during the past three fiscal years are described in Note 7 to the Notes
to the Financial Statements contained under Item 8.


                                       3


<PAGE>   4
ITEM 6. SELECTED FINANCIAL DATA


<TABLE>
<CAPTION>
                                                     FOR THE YEAR ENDED DECEMBER 31,
                            ------------------------------------------------------------------------------
                               1997             1996             1995             1994            1993
                            ----------       ----------       ----------       ----------       ----------
<S>                         <C>              <C>              <C>              <C>              <C>       
Rental Revenue              $  327,956       $  361,980       $  275,561       $  273,076       $  259,530

Interest and
 other income                    2,326            1,244            1,193            1,792            2,221

Net income                     187,583          219,223          134,697          135,669          127,455

Net income
 per Limited
 Partnership
 Unit (1)                         1.12             1.31              .81              .81              .76

Cash Distributions
 per Limited
 Partnership
 Unit (2)(3)(4)(5)(6)             1.70             1.74             1.45             2.00              .61

Total Assets                 2,334,746        2,429,366        2,495,331        2,603,405        2,807,793

Long-term
 Obligations                   137,953          137,953          137,953          137,953          137,953
</TABLE>


(1)      The net income per Limited Partnership Unit was calculated based upon
         165,415 weighted average Units outstanding for all years presented.

(2)      Two quarterly distributions were disbursed during the year ended
         December 31, 1993. Cash distributions for the quarters ended September
         30, 1993 and December 31, 1993 amounted to $.83 and were paid January
         31, 1994 and February 2, 1994, respectively.

(3)      Cash distributions for the quarter ended December 31, 1994 amounted to
         $.40 per Limited Partnership Unit and were paid January 17, 1995. Five
         quarterly distributions were disbursed during the year ended December
         31, 1994.

(4)      Cash distributions for the quarter ended December 31, 1995 amounted to
         $.40 per Limited Partnership Unit and were paid January 17, 1996. Four
         distributions were disbursed during the year ended December 31, 1995.


                                       4


<PAGE>   5
ITEM 6. SELECTED FINANCIAL DATA - CONTINUED

(5)      Cash distributions for the quarter ended December 31, 1996 amounted to
         $.41 per Limited Partnership Unit and were paid January 31, 1997. Four
         distributions were disbursed during the year ended December 31, 1996.

(6)      Cash distributions for the quarter ended December 31, 1997 amounted to
         $.41 per Limited Partnership Unit and were paid January 31, 1998. Four
         quarterly distributions were disbursed during the year ended December
         31, 1997.

ITEM 7. MANAGEMENT'S DISCUSSION AND ANALYSIS OF FINANCIAL CONDITION AND RESULTS
        OF OPERATIONS

Liquidity and Capital Resources

The Registrant commenced offering of Limited Partnership Units on June 5, 1987.
By June 3, 1988, the sale of such Units provided a total capitalization for the
Registrant of $4,135,375 including $1,000 attributable to the Special Limited
Partner. 14.5 percent of the cash received from the sale of Limited Partnership
Units was used to pay commissions to brokers and to reimburse the General
Partner for offering costs incurred. Approximately $3,000,000 of the remaining
funds were expended for the acquisition of sites and construction of three
restaurants. During 1989, the first restaurant opened for business. The two
additional restaurants commenced operation in 1990. In February 1992, the
Registrant distributed to Limited Partners of record on December 31, 1991
$442,270 of net proceeds not utilized as reserves and not invested in
properties.

Since the three restaurants owned by the Registrant opened, cash flow from lease
payments received from Del Taco, the Registrant's General Partner, which leases
all three restaurants, has provided adequate liquidity for operation of the
Registrant. However, the Registrant's overwhelmingly predominant source of
income to meet its expenses and fund distributions to its Limited Partners is
payments from Del Taco under the Leases, comprising primarily rent calculated on
the basis of the gross sales of the restaurants operated on the Properties, as
to which there are no contractually specified minimum or guaranteed amounts.
Thus, the adequacy of the Registrant's liquidity and capital resources in the
future will depend primarily upon the gross revenues of such restaurants as well
as upon Del Taco's financial condition and results of operations generally.

Results of Operations

The Registrant owns three Properties that are under long-term lease to Del Taco
for restaurant operations (Del Taco, in turn, has sub-leased one of the
restaurants to a Del Taco franchisee). The Registrant receives rental revenues
equal to 12 percent of restaurant sales. The Registrant had rental revenue of
$327,956 for the year ended December 31, 1997, representing a decrease from the
rental revenues of $361,980 in 1996. Such decrease is directly attributable to
the earning of supplemental rent in 1996.


                                       5


<PAGE>   6
Results of Operations - Continued

The Following table sets forth rental revenue earned by restaurant for the year:


<TABLE>
<CAPTION>
                                                       YEAR ENDED
                                                       DECEMBER 31,
                                         --------------------------------------
                                           1997           1996           1995
                                         --------       --------       --------
<S>                                      <C>            <C>            <C>     
Orangethorpe Ave., Placentia, CA         $142,585       $163,697       $126,296

Lakeshore Drive, Lake Elsinore, CA        119,218        130,479         96,555

Highland Ave., San Bernardino, CA          66,153         67,804         52,710
                                         --------       --------       --------

            Total                        $327,956       $361,980       $275,561
                                         ========       ========       ========
</TABLE>


The following table sets forth, for the periods indicated, the percentage
relationship to total general and administrative expenses of items included in
the Registrant's Statements of Income:

                               Percentage of Total General & Admin. Expense


<TABLE>
<CAPTION>
                                     Year Ended
                                    December 31,
                         ----------------------------------
                          1997          1996          1995
                         ------        ------        ------
<S>                      <C>           <C>           <C>   
Accounting fees           38.00%        41.12%        41.57%
Distribution of
  information to
  Limited Partners        59.95         55.77         55.85
Other                      2.05          3.11          2.58
                         ------        ------        ------
                          100.0%       100.00%       100.00%
                         ======        ======        ======
</TABLE>


Operating expenses include general and administrative expenses which consist
primarily of accounting fees and costs of distribution of information to the
Limited Partners. For the years ended December 31, general and administrative
expenses decreased from $40,251 in 1996 to $38,951 in 1997 reflecting lower
costs for accounting and administration of the partnership. The Registrant
incurred depreciation expense of $103,748, $103,750 and $103,750 for each of the
years ended December 31, 1997, 1996 and 1995.

For the reasons stated under "Liquidity and Capital Resources" above, the
Registrant's result of operations in the future will depend primarily upon the
gross revenues of the restaurants located on the Properties leased to Del Taco
as well as upon Del Taco's financial condition and results of operations
generally.

Management does not believe the operations of the Company will be significantly
impacted by the year 2000 software issue and does not believe the year 2000
software issue will materially effect the Company's operations, financial
position or cash flows.


                                       6


<PAGE>   7
ITEM 8.  FINANCIAL STATEMENTS


PART I.  INFORMATION


<TABLE>
<CAPTION>
     INDEX                                                PAGE NUMBER
     -----                                                -----------
<S>                                                       <C>
Report of Independent Public Accountants                       8

Balance Sheets at December 31, 1997 and 1996                   9

Statements of Income for the years ended
  December 31, 1997, 1996 and 1995                             10

Statement of Changes in Partners' Equity for
  the three years ended December 31, 1997                      11

Statements of Cash Flows for the years ended
  December 31, 1997, 1996 and 1995                             12

Notes to Financial Statements                                 13-17
</TABLE>


                                       7


<PAGE>   8
                        [ARTHUR ANDERSON LLP LETTERHEAD]


                    REPORT OF INDEPENDENT PUBLIC ACCOUNTANTS


To the Partners of
 Del Taco Restaurant Properties, IV:


We have audited the accompanying balance sheets of DEL TACO RESTAURANT
PROPERTIES IV (a California limited partnership) as of December 31, 1997 and
1996, and the related statements of income, changes in partners' equity and cash
flows for each of three years in the period ended December 31, 1997. These
financial statements are the responsibility of the Partnership's management. Our
responsibility is to express an opinion on these financial statements based on
our audits.

We conducted our audits in accordance with generally accepted auditing
standards. Those standards require that we plan and perform the audit to obtain
reasonable assurance about whether the financial statements are free of material
misstatement. An audit includes examining, on a test basis, evidence supporting
the amounts and disclosures in the financial statements. An audit also includes
assessing the accounting principles used and significant estimates made by
management, as well as evaluating the overall financial statement presentation.
We believe that our audits provide a reasonable basis for our opinion.

In our opinion, the financial statements referred to above present fairly, in
all material respects, the financial position of Del Taco Restaurant Properties
IV as of December 31, 1997 and 1996, and the results of its operations and its
cash flows, for each of the three years in the period ended December 31, 1997,
in conformity with generally accepted accounting principles.

Our audit was made for the purpose of forming an opinion on the basic financial
statements taken as a whole. The schedule in the index of financial statements
is presented for purposes of complying with the Securities and Exchange
Commissions rules and is not part of the basic financial statements. This
schedule has been subjected to the auditing procedures applied in the audit of
the basic financial statements and, in our opinion, fairly states, in all
material respects, the financial data required to be set forth therein in
relation to the basic financial statements taken as a whole.


                                             /s/ ARTHUR ANDERSEN LLP
                                             -----------------------
                                                 Arthur Andersen LLP

Orange County, California
February 10, 1998

                                       8
<PAGE>   9
                          DEL TACO INCOME PROPERTIES IV

                                 BALANCE SHEETS


<TABLE>
<CAPTION>
                                                                           DECEMBER 31,
                                                                  ------------------------------
                                                                     1997               1996
                                                                  -----------        -----------
<S>                                                               <C>                <C>        
                                     ASSETS

CURRENT ASSETS:
  Cash                                                            $    75,411        $    79,857
  Receivable from Del Taco, Inc. (Note 5)                              65,132             51,558
  Deposits                                                                400                400
                                                                  -----------        -----------
     Total current assets                                             140,943            131,815
                                                                  -----------        -----------

PROPERTY AND EQUIPMENT, AT COST (NOTE 1)
  Land and improvements                                             1,236,700          1,236,700
  Buildings and improvements                                        1,289,860          1,289,860
  Machinery and equipment                                             484,789            484,789
                                                                  -----------        -----------
                                                                    3,011,349          3,011,349
    Less: accumulated depreciation                                    817,546            713,798
                                                                  -----------        -----------
                                                                    2,193,803          2,297,551
                                                                  -----------        -----------

                                                                  $ 2,334,746        $ 2,429,366
                                                                  ===========        ===========

                        LIABILITIES AND PARTNERS' EQUITY

CURRENT LIABILITIES:
  Payable to Limited Partners                                     $     2,503        $     3,038
  Accounts Payable                                                      6,130              3,000
                                                                  -----------        -----------
     Total current liabilities                                          8,633              6,038
                                                                  -----------        -----------

OBLIGATION TO GENERAL PARTNER (NOTE 3)                                137,953            137,953

PARTNERS' EQUITY (NOTE 2)
  Limited Partners                                                  2,197,413          2,293,656
  General Partner - Del Taco, Inc.                                     (9,253)            (8,281)
                                                                  -----------        -----------
                                                                    2,188,160          2,285,375
                                                                  -----------        -----------

                                                                  $ 2,334,746        $ 2,429,366
                                                                  ===========        ===========
</TABLE>

                     The accompanying notes are an integral
                       part of these financial statements.


                                       9


<PAGE>   10
                          DEL TACO INCOME PROPERTIES IV

                              STATEMENTS OF INCOME


<TABLE>
<CAPTION>
                                                YEAR ENDED
                                                DECEMBER 31,
                                   --------------------------------------
                                     1997           1996           1995
                                   --------       --------       --------
<S>                                <C>            <C>            <C>     
REVENUES:
  Rent (Note 4)                    $327,956       $361,980       $275,561
  Interest                            1,651          1,194          1,068
  Other                                 675             50            125
                                   --------       --------       --------
                                    330,282        363,224        276,754
                                   --------       --------       --------
EXPENSES:
  General and administrative         38,951         40,251         38,307
  Depreciation                      103,748        103,750        103,750
                                   --------       --------       --------
                                    142,699        144,001        142,057
                                   --------       --------       --------

Net Income                         $187,583       $219,223       $134,697
                                   ========       ========       ========

Net Income per Limited
  Partnership Unit (Note 1)        $   1.12       $   1.31       $    .81
                                   ========       ========       ========
</TABLE>


                          The accompanying notes are an
                  integral part of these financial statements.


                                       10


<PAGE>   11
                          DEL TACO INCOME PROPERTIES IV

                    STATEMENT OF CHANGES IN PARTNERS' EQUITY

                       THREE YEARS ENDED DECEMBER 31, 1997


<TABLE>
<CAPTION>
                                          Limited Partners       
                                   ------------------------------         General
                                      Units             Amount             Partner             Total
                                   -----------        -----------        -----------        -----------
<S>                                <C>                <C>                <C>                <C>        
Balance, December 31, 1994             165,415        $ 2,469,723        $    (6,507)       $ 2,463,216

 Net income                                               133,350              1,347            134,697

 Cash distributions (Note 7)                             (240,586)            (2,426)          (243,012)
                                   -----------        -----------        -----------        -----------

Balance, December 31, 1995             165,415          2,362,487             (7,586)         2,354,901

 Net income                                               217,031              2,192            219,223

 Cash distributions (Note 7)                             (285,862)            (2,887)          (288,749)
                                   -----------        -----------        -----------        -----------

Balance, December 31, 1996             165,415          2,293,656             (8,281)         2,285,375

 Net income                                               185,707              1,876            187,583

 Cash distributions (Note 7)                             (281,950)            (2,848)          (284,798)
                                   -----------        -----------        -----------        -----------

Balance, December 31, 1997             165,415        $ 2,197,413        $    (9,253)       $ 2,188,160
                                   ===========        ===========        ===========        ===========
</TABLE>


                     The accompanying notes are an integral
                       part of these financial statements.


                                       11


<PAGE>   12
                          DEL TACO INCOME PROPERTIES IV

                            STATEMENTS OF CASH FLOWS


<TABLE>
<CAPTION>
                                                                                  YEAR ENDED
                                                                                 DECEMBER 31,
                                                                  -------------------------------------------
                                                                    1997             1996             1995
                                                                  ---------        ---------        ---------
<S>                                                               <C>              <C>              <C>      
CASH FLOWS FROM OPERATING ACTIVITIES:

Net Income                                                        $ 187,583        $ 219,223        $ 134,697
Adjustments to reconcile net income to net cash provided by
operating activities:
  Depreciation                                                      103,748          103,750          103,750
  Increase (decrease) in payable to
   Limited Partner                                                     (535)           1,387             (583)
  (Increase) decrease in receivable
   from General Partner                                             (13,574)         (31,471)           2,909
  Increase in accounts payable                                        3,130            2,175              825
                                                                  ---------        ---------        ---------

    Net cash provided by operating
     activities                                                     280,352          295,064          241,598


CASH FLOWS FROM FINANCING ACTIVITIES:

Cash distributions to partners                                     (284,798)        (288,749)        (243,012)
                                                                  ---------        ---------        ---------

Net increase (decrease) in cash                                      (4,446)           6,315           (1,414)

Beginning cash balance                                               79,857           73,542           74,956
                                                                  ---------        ---------        ---------

Ending cash balance                                               $  75,411        $  79,857        $  73,542
                                                                  =========        =========        =========
</TABLE>


                     The accompanying notes are an integral
                       part of these financial statements.


                                       12


<PAGE>   13
                          DEL TACO INCOME PROPERTIES IV

                          NOTES TO FINANCIAL STATEMENTS

                                DECEMBER 31, 1997


NOTE 1 - ORGANIZATION AND SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES

THE PARTNERSHIP: Del Taco Income Properties IV (a California limited
partnership) was formed on March 23, 1987, for the purpose of acquiring real
property in California for construction of three Mexican-American restaurants to
be leased under long-term agreements to Del Taco, Inc. (General Partner for
operation under the Del Taco trade name). As of July 13, 1990, all three
restaurants had commenced operation on acquired properties.

BASIS OF ACCOUNTING: The Partnership utilizes the accrual method of accounting
for transactions relating to the business of the Partnership. Distributions are
made to the General and Limited Partners in accordance with the provisions of
the Partnership Agreement (see Note 2).

PROPERTY AND EQUIPMENT: Property and equipment is stated at cost. Depreciation
is computed using the straight-line method over estimated useful lives which are
20 years for land improvements, 35 years for buildings and improvements, and 10
years for machinery and equipment.

In fiscal 1996, the Registrant adopted Statement of Financial Accounting
Standards (SFAS) No. 121, "Accounting for the Impairment of Long Lived Assets
and for Long Lived Assets to be Disposed of." SFAS 121 requires that long-lived
assets be reviewed for impairment whenever events or changes in circumstances
indicate that the carrying value of the asset may not be recoverable. In
evaluating long-lived assets held for use, an impairment loss is recognized if
the sum of the expected future cash flows (undiscounted and without interest
charges) is less than the carrying value of the asset. Once a determination has
been made that an impairment loss should be recognized for long-lived assets,
various assumptions and estimates are used to determine fair value including,
among others, estimated costs of construction and development, recent sales of
comparable properties and the opinions of fair value prepared by independent
real estate appraisers. Long-lived assets to be disposed of are reported at the
lower of carrying amount or fair value less cost to sell.

The adoption of SFAS No. 121 did not have a material effect on the Registrant's
financial statements.

INCOME TAXES: No provision has been made for federal or state income taxes on
Partnership net income, since the Partnership is not subject to income tax.
Partnership income is includable in the taxable income of the individual
partners as required under applicable income tax laws. Certain items, primarily
related to depreciation methods, are accounted for differently for income tax
reporting purposes (see Note 6).


                                       13


<PAGE>   14
DEL TACO INCOME PROPERTIES IV
NOTES TO FINANCIAL STATEMENTS - CONTINUED
DECEMBER 31, 1997


NOTE 1 - ORGANIZATION AND SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES -
         CONTINUED

NET INCOME PER LIMITED PARTNERSHIP UNIT: Net income per Limited Partnership Unit
is calculated based upon 165,415 weighted average Units outstanding for all
years presented.

USE OF ESTIMATES: The preparation of the financial statements in conformity with
generally accepted accounting principles requires management to make certain
estimates and assumptions that affect the reported amounts of assets and
liabilities at the date of the financial statements and the reported amounts of
revenues and expenses during the reporting period. Actual results could differ
from those estimates.

NOTE 2 - PARTNERS' EQUITY

Pursuant to the Partnership Agreement, annual partnership net income or loss is
allocated one percent to the General Partner and 99 percent to the Limited
Partners. Partnership gains from any sale or refinancing will be allocated one
percent to the General Partner and 99 percent to the Limited Partners until
allocated gains and profits equal losses, distributions and syndication costs,
and until each class of Limited Partners receive their priority return as
defined in the Partnership Agreement. Additional gains will be allocated 12
percent to the General Partner and 88 percent to the Limited Partners.

NOTE 3 - SITE SELECTION AND DEVELOPMENT FEE

Under terms of the Partnership Agreement, the General Partner is entitled to
receive a fee in an amount equal to five percent of the gross proceeds of the
offering. The fee shall be for services rendered in connection with site
selection and the design and supervision of construction of improvements to
acquired properties. One percent of the gross proceeds of the offering has been
paid to the General Partner. The remaining four percent of this fee shall be
earned at the time the services are rendered, but shall not be paid and shall be
subordinated to the Limited Partners' interests until all restaurants have
opened and the Limited Partners have received certain minimum returns on their
investment, as required by the Partnership Agreement. It is the policy of the
Partnership to accrue the site selection and development fee as an obligation to
the General Partner. No fees were earned for such services during 1997, 1996 and
1995.


                                       14


<PAGE>   15
DEL TACO INCOME PROPERTIES IV
NOTES TO FINANCIAL STATEMENTS - CONTINUED
DECEMBER 31, 1997


NOTE 4 - LEASING ACTIVITIES

The Registrant leases certain properties for operation of restaurants to Del
Taco, Inc. (General Partner) on a triple net basis. The leases are for terms of
32 years commencing with the completion of the restaurant facility located on
each property and require monthly rentals equal to 12 percent of the gross sales
of the restaurants. There is no minimum rental under any of the leases. The
Registrant had a total of three Properties leased to Del Taco as of December 31,
1997, 1996 and 1995 (Del Taco, in turn, has subleased one of the restaurants to
a Del Taco franchisee).

The two restaurants operated by Del Taco, for which the Registrant is the
lessor, had combined, unaudited sales of $1,523,099, $1,452,047, $1,491,715 and
unaudited net income of $76,600, $68,556 and $96,253 for the years ended
December 31, 1997, 1996 and 1995, respectively. Net income by restaurant
includes charges for general and administrative expenses incurred in connection
with supervision of restaurant operations and interest expense. The one
restaurant operated by a Del Taco franchisee, for which the Registrant is the
lessor, had unaudited sales of $874,554, $835,362 and $804,624 for the years
ended December 31, 1997, 1996 and 1995, respectively.

The Highland Avenue restaurant in Highland (San Bernardino), California had
unaudited net losses of $4,311, $14,043 and $10,904 for the years ended December
31, 1997, 1996 and 1995, respectively.

NOTE 5 - RELATED PARTIES

The receivable from Del Taco consists of rent accrued for the month of December
1997 as well as supplemental rent. These amounts were collected on January 17,
1998.

The General Partner received $2,848 in distributions relating to its one percent
interest in the Registrant for the year ended December 31, 1997.

Del Taco, Inc. serves in the capacity of general partner in other partnerships
which are engaged in the business of operating restaurants, and three other
partnerships which were formed for the purpose of acquiring real property in
California for construction of Mexican-American restaurants for lease under
long-term agreements to Del Taco, Inc. for operation under the Del Taco trade
name.


                                       15


<PAGE>   16
DEL TACO INCOME PROPERTIES IV
NOTES TO FINANCIAL STATEMENTS - CONTINUED
DECEMBER 31, 1997


NOTE 5 - RELATED PARTIES - CONTINUED

Partners Network Corp., a California corporation ("PNC"), which is wholly-owned
by the same principals who own the Dealer Manager, who was primarily responsible
for selling Limited Partnership Units, is the Special Limited Partner of the
Partnership, as defined in the Partnership Agreement. PNC will monitor the
Partnership investments and perform services in connection with the disposition
of properties in the future. In return for such services, PNC will be entitled
to receive certain subordinated distributions and payments.

NOTE 6  - INCOME TAXES

A reconciliation of financial statement net income to taxable income for each of
the periods is as follows:


<TABLE>
<CAPTION>
                                            1997           1996           1995
                                          --------       --------       --------
<S>                                       <C>            <C>            <C>     
Net income per financial statements       $187,582       $219,223       $134,697

Excess book depreciation                    48,537         27,151         20,124
                                          --------       --------       --------

Taxable income                            $236,119       $246,374       $154,821
                                          ========       ========       ========
</TABLE>


A reconciliation of partnership equity per the financial statements to net worth
for tax purposes as of December 31, 1997, is as follows:


<TABLE>
<S>                                        <C>       
Partners' equity per financial
  statements                               $2,188,159

Issue costs of Limited Partnership
  Units capitalized for tax purposes          579,259

Excess tax depreciation                         9,967
                                           ----------
Net worth for tax purposes                 $2,777,385
                                           ==========
</TABLE>


                                       16


<PAGE>   17
DEL TACO INCOME PROPERTIES IV
NOTES TO FINANCIAL STATEMENTS - CONTINUED
DECEMBER 31, 1997


NOTE 7 - CASH DISTRIBUTIONS TO LIMITED PARTNERS

Cash distributions paid to Limited Partners for the three years ended December
31, 1997 were as follows:


<TABLE>
<CAPTION>
                                                   Weighted         Number of Units
                        Distributions per       Average Number       Outstanding at
                       Limited Partnership         of Units            the End of
Quarter Ended                 Unit               Outstanding            Quarter
-------------          -------------------      --------------      ---------------
<S>                    <C>                      <C>                 <C>

December 31, 1994          $    .40                  165,415            165,415
March 31, 1995                  .33                  165,415            165,415
June 30, 1995                   .31                  165,415            165,415
September 30, 1995              .41                  165,415            165,415
                           --------                                     
  Total paid in 1995       $   1.45                                     
                           ========                                     
                                                                        
December 31, 1995          $    .40                  165,415            165,415
March 31, 1996                  .32                  165,415            165,415
June 30, 1996                   .65                  165,415            165,415
September 30, 1996              .37                  165,415            165,415
                           --------                                     
  Total paid in 1996       $   1.74                                     
                           ========                                     
                                                                        
December 31, 1996               .41                  165,415            165,415
March 31, 1997                  .49                  165,415            165,415
June 30, 1997                   .37                  165,415            165,415
September 30, 1997              .43                  165,415            165,415
                           --------                                             
  Total paid in 1997       $   1.70                                
                           ========
</TABLE>

Cash distributions per Limited Partnership Unit were calculated based upon the
weighted average number of units outstanding for each quarter and were paid from
operations. Cash distributions for the quarter ended December 31, 1997 amounted
to $.41 per Limited Partnership Unit and were paid January 31, 1998.


                                       17


<PAGE>   18
                                    PART III


ITEM 9.   DISAGREEMENTS ON ACCOUNTING AND FINANCIAL DISCLOSURE

None

ITEM 10.  DIRECTORS AND EXECUTIVE OFFICERS OF THE REGISTRANT'S GENERAL
          PARTNER

(a) & (b) The executive officers and directors of the General Partner and their
ages are set forth below:


<TABLE>
<CAPTION>
Name                    Title                                          Age
----                    -----                                          ---
<S>                     <C>                                            <C>
Kevin K. Moriarty       Director, Chairman and Chief Executive Officer  51

Paul W. Hitzelberger    Executive Vice President, Brand Strategy and
                        Franchise Relations/Development                 53

Robert J. Terrano       Executive Vice President and
                         Chief Financial Officer                        42

James D. Stoops         Executive Vice President, Operations            45

Janet D. Simmons        Senior Vice President, Purchasing               41

Michael L. Annis        Vice President, Secretary and General Counsel   51

C. Douglas Mitchell     Vice President and Corporate Controller         47
</TABLE>


The above referenced executive officers and directors of the General Partner
will hold office until the annual meeting of its shareholders and directors,
which is scheduled for the later part of 1998.

(c)      None

(d)      No family relationship exists between any such director or executive
         officer of the General Partner.

(e)      The following is an account of the business experience during the past
         five years of each such director and executive officer:


                                       18


<PAGE>   19
Kevin K. Moriarty, Director, Chairman and Chief Executive Officer of Del Taco,
Inc. Mr. Moriarty began his career with Burger King Corporation in 1974 in
Operations Unit Management. In 1983, he was promoted to Area Manager in New
York, and was subsequently promoted to the Regional Vice President, Chicago
Region in 1985. In 1988, he became Executive Vice President and General Manager
of the North Central Division. Mr. Moriarty served in that position until 1990
when he joined Del Taco, Inc. as President and Chief Executive Officer on July
31, 1990. Mr. Moriarty has served as a Director of the General Partner since
1990.

Paul W. Hitzelberger, Executive Vice President, Brand Strategy and Franchise
Relations/Development of Del Taco, Inc. He was appointed to his current position
in December 1995. Mr. Hitzelberger has responsibility for franchise development,
relations and training and will oversee public relations and training for the
corporation. From 1991 to 1995, Mr. Hitzelberger was Executive Vice President,
Marketing of Del Taco, Inc. From September 1988 through September 1989, Mr.
Hitzelberger was Chief Executive Officer of Environmental Marketing Group. Prior
to that, Mr. Hitzelberger was a Vice President of Del Taco, Inc. Prior to
joining Del Taco, Inc., he served as Vice President - Marketing at the
department store division of Lucky Stores, Inc., a major supermarket retailer.
Prior to his position with Lucky, Mr. Hitzelberger held various positions in
marketing and retailing at Wallpapers to Go, Inc., a division of General Mills,
Inc., and Coast to Coast Stores, Inc. a subsidiary of Household Merchandising,
Inc. Mr. Hitzelberger received a Master of Business Administration degree from
Loyola University in Chicago, Illinois.

Robert J. Terrano, Executive Vice President and Chief Financial Officer of Del
Taco, Inc. From May 1994 to April 1995, Mr. Terrano served as Chief Financial
Officer for Denny's, Inc. in Spartanburg, S.C. From August 1983 to May 1994, he
served with Burger King Corporation, Miami Florida, in a variety of positions,
most recently as Division Controller. Mr. Terrano joined Del Taco, Inc. in April
1995.

James D. Stoops, Executive Vice President, Operations of Del Taco, Inc. From
1968 to 1991, Mr. Stoops served in a wide variety of Operations positions with
Burger King Corporation with increasing levels of responsibility. In 1985, Mr.
Stoops was appointed Region Vice President/General Manager for the New York
region and served in that position until October of 1990. In January of 1991, he
joined Del Taco, Inc. in his current post.

Janet D. Simmons, Senior Vice President, Purchasing of Del Taco, Inc. From 1979
to 1986, Ms. Simmons was with Denny's Inc. She served in the Research and
Development department in a variety of positions until 1982 when she was
promoted to the position of Purchasing Agent. Ms. Simmons was hired in 1986 as
Manager of Contract Purchasing with Carl Karcher Enterprises, a post she held
until March 1990 when she became Vice President, Purchasing for Del Taco, Inc.
Ms. Simmons has a Bachelor of Science degree in Foods and Nutrition from Cal
State Polytechnic University in Pomona, California.


                                       19


<PAGE>   20
Michael L. Annis, Vice President, Secretary and General Counsel of Del Taco,
Inc. From 1981 to 1986 Mr. Annis served as Regional Real Estate Manager and
Director of Real Estate Services with Taco Bell, Inc. In 1986 he served as
Regional General Manager with Quaker State Minit Lube. In January of 1987 Mr.
Annis joined Red Robin International, Inc. as General Counsel and was
subsequently promoted to Vice President/Secretary and later Vice President Real
Estate Development/Secretary and General Counsel, the position he held until
joining Del Taco, Inc. in December of 1993. Mr. Annis received his J.D. Degree
from Whittier College.

C. Douglas Mitchell, Vice President and Corporate Controller. Mr. Mitchell
joined Del Taco, Inc. in August of 1994 as Controller and was promoted to his
current position in January 1996. From 1990 to 1994, Mr. Mitchell was a Senior
Audit Manager with Coopers & Lybrand. Prior to 1990, Mr. Mitchell held various
positions in finance and accounting with the Geneva Companies (a subsidiary of
Chemical Bank), Zaremba Corporation (a real estate developer) and The Dexter
Corporation (an international manufacturer of specialty materials). Mr. Mitchell
has a Bachelor of Science degree with a major in accounting from the University
of Southern California.

ITEM 11. MANAGEMENT REMUNERATION AND TRANSACTIONS

The Registrant has no executive officers or directors and pays no direct
remuneration to any executive officer or director of its General Partner. The
Registrant has not issued any options or stock appreciation rights to any
executive officer or director of its General Partner, nor does the Registrant
propose to pay any annuity, pension or retirement benefits to any executive
officer or director of its General Partner. The Registrant has no plan, nor does
the Registrant presently propose a plan, which will result in any remuneration
being paid to any executive officer or director of the General Partner upon
termination of employment.

ITEM 12. SECURITY OWNERSHIP OF CERTAIN BENEFICIAL OWNERS AND MANAGEMENT

(a)      No person of record currently owns more than five percent of Limited
         Partnership Units of the Registrant, nor was any person known of by the
         Registrant to own of record and beneficially, or beneficially only,
         more than five percent of such securities.

(b)      Neither Del Taco, Inc., nor any executive officer or director of Del
         Taco, Inc. owns any Limited Partnership Units of the Registrant.

(c)      The Registrant knows of no contractual arrangements, the operation or
         the terms of which may at a subsequent date result in a change in
         control of the Registrant, except for provisions in the Partnership
         Agreement providing for removal of the General Partner by holders of a
         majority of the Limited Partnership Units and if a material event of
         default occurs under the financing agreements of the General Partner.


                                       20


<PAGE>   21
ITEM 13.  CERTAIN RELATIONSHIPS AND RELATED TRANSACTIONS

(a)      No transactions have occurred between the Registrant and any executive
         officer or director of its General Partner.

         During 1997, the following transactions occurred between the Registrant
         and the General Partner pursuant to the terms of the Partnership
         Agreement.

         (1)      The General Partner earned $1,876 as its one percent share of
                  the net income of the Registrant.

         (2)      The General Partner received $2,848 in distributions relating
                  to its one percent interest in the Registrant.

(b)      During 1997, the Registrant had no business relationships with any
         entity of a type required to be reported under this item.

(c)      Neither the General Partner, any director or officer of the General
         Partner or any associate of any such person, was indebted to the
         Registrant at any time during 1997 for any amount in excess of $60,000.

(d)      Not applicable.


                                       21


<PAGE>   22
                                     PART IV


ITEM 14(A)(1) AND (2).  EXHIBITS, FINANCIAL STATEMENTS SCHEDULES, AND
                        REPORTS ON FORM 8-K

         Financial statement schedules:

               Schedule III - Real Estate and Accumulated Depreciation

         Financial statement schedules other than those referred to above have
         been omitted because they are not applicable or not required.

(b)      No reports on Form 8-K were filed during the last quarter of 1997.

(c)      Exhibits required by Item 601 of Regulation S-K:

         1.       Incorporated herein by reference, Restated Agreement of
                  Limited Partnership of Del Taco Income Properties IV filed as
                  Exhibit 3.01 to Registrant's Registration Statement on Form
                  S-11 as filed with the Securities and Exchange Commission on
                  June 5, 1987.

         2.       Incorporated herein by reference, Amendment to Restated
                  Agreement of Limited Partnership of Del Taco Income Properties
                  IV.

         3.       Incorporated herein by reference, Form of Standard Lease to be
                  entered into by Registrant and Del Taco, Inc., as lessee,
                  filed as Exhibit 10.02 to Registrant's Registration Statement
                  on Form S-11 as filed with the Securities and Exchange
                  Commission on June 5, 1987.


                                       22


<PAGE>   23
                           DEL TACO IV - SCHEDULE III
                    REAL ESTATE AND ACCUMULATED DEPRECIATION
                                DECEMBER 31, 1997


<TABLE>
<CAPTION>
                                                                      Cost capitalized    Gross amount at
                                                  Initial cost          subsequent to     which carried at              
           Description             Encumbrances    to company            acquisition      close of period
                                                 --------------------------------------------------------   Accumulated
                                                  Buildings                              Buildings & land   depreciation
        (All Restaurants)                          & land        Improve-     Carrying     improvements                 
                                                 improvements     ments        costs           Total                    
                                    ----------   -----------    ----------   -----------     -----------      ---------
<S>                                 <C>          <C>            <C>          <C>         <C>                <C>       
Placentia, CA                       $        -   $   465,933    $  485,961   $         -     $   951,894      $ 163,337 
Lake Elsinore, CA                            -       449,058       468,361             -         917,419        157,422 
San Bernardino, CA                           -       321,709       335,538             -         657,247        112,778 
                                    ----------   -----------    ----------   -----------     -----------      ---------
                                                                                       -
                                    $        -   $ 1,236,700    $1,289,860   $         -     $ 2,526,560      $ 433,537
                                    ==========   ===========    ==========   ===========     ===========      =========

</TABLE>

<TABLE>
<CAPTION>
                                                                                  Life on which        
           Description                    Date of            Date            depreciation in latest    
                                       construction       acquired             income statement        
        (All Restaurants)                                                        is computed           
                                       ------------       --------           ----------------------    
<S>                                    <C>                <C>                <C>
Placentia, CA                              1988             1988               20 (LI), 35 (BI)        
Lake Elsinore, CA                          1989             1989               20 (LI), 35 (BI)        
San Bernardino, CA                         1989             1989               20 (LI), 35 (BI)        
</TABLE>


<TABLE>
<CAPTION>
                                                                                                            Accumulated
                                                                                             Restaurants    Depreciation
                                                                                             -----------    ------------
 <S>                                                                                         <C>             <C>
Balances at December 31, 1994:                                                               $ 2,526,560      $ 267,733
   Acquisitions                                                                                        -         55,268
   Sales                                                                                               -              -
                                                                                             -----------      ---------
Balances at December 31, 1995:                                                                 2,526,560        323,001
   Acquisitions                                                                                        -         55,268
   Sales                                                                                               -              -
                                                                                             -----------      ---------
Balances at December 31, 1996:                                                                 2,526,560        378,269
   Acquisitions                                                                                        -         55,268
   Sales                                                                                               -              -
                                                                                             -----------      ---------
Balances at December 31, 1997:                                                               $ 2,526,560      $ 433,537
                                                                                             ===========      =========
</TABLE>








                                       23
<PAGE>   24
                                   SIGNATURES


Pursuant to the requirements of Section 13 or 15(d) 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.



                                            DEL TACO INCOME PROPERTIES IV
                                            a California limited partnership
                                            Registrant

                                            Del Taco, Inc.
                                            General Partner


                                            
Date March 07, 1998                         Kevin K. Moriarty
     --------------                         -----------------------------------
                                            Kevin K. Moriarty
                                            Director, Chairman and Chief
                                            Executive Officer



Date March 07, 1998                         Michael L. Annis
     --------------                         -----------------------------------
                                            Michael L. Annis
                                            Vice President, Secretary and
                                            General Counsel




Date March 07, 1998                         Robert J. Terrano
     --------------                         -----------------------------------
                                            Robert J. Terrano
                                            Executive Vice President and
                                            Chief Financial Officer




Date March 07, 1998                         C. Douglas Mitchell
     --------------                         -----------------------------------
                                            C. Douglas Mitchell
                                            Vice President and Corporate
                                            Controller


                                       24


<PAGE>   25
[ARTICLE] 5
<TABLE>
<S>                             <C>
[PERIOD-TYPE]                   12-MOS
[FISCAL-YEAR-END]                          DEC-31-1997
[PERIOD-START]                             JAN-01-1997
[PERIOD-END]                               DEC-31-1997
[CASH]                                          75,411
[SECURITIES]                                       400
[RECEIVABLES]                                   65,132
[ALLOWANCES]                                         0
[INVENTORY]                                          0
[CURRENT-ASSETS]                               140,943
[PP&E]                                       3,011,349
[DEPRECIATION]                                 817,546
[TOTAL-ASSETS]                               2,334,746
[CURRENT-LIABILITIES]                            8,633
[BONDS]                                              0
[PREFERRED-MANDATORY]                                0
[PREFERRED]                                          0
[COMMON]                                             0
[OTHER-SE]                                   2,188,160
[TOTAL-LIABILITY-AND-EQUITY]                 2,334,746
[SALES]                                              0
[TOTAL-REVENUES]                               330,282
[CGS]                                                0
[TOTAL-COSTS]                                  142,699
[OTHER-EXPENSES]                                     0
[LOSS-PROVISION]                                     0
[INTEREST-EXPENSE]                                   0
[INCOME-PRETAX]                                187,583
[INCOME-TAX]                                         0
[INCOME-CONTINUING]                            187,583
[DISCONTINUED]                                       0
[EXTRAORDINARY]                                      0
[CHANGES]                                            0
[NET-INCOME]                                   187,583
[EPS-PRIMARY]                                     1.12
[EPS-DILUTED]                                     1.12
</TABLE>