8-K 1 mab04op1_jul.txt JULY 8K UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington D. C. 20549 Form 8-K Current Report Pursuant to Section 13 or 15(d) of The Securities Exchange Act of 1934 Date of Report (Date of earliest event reported): July 26, 2004 MASTR ASSET BACKED SECURITIES TRUST Mortgage Pass-Through Certificates, Series 2004-OPT1 Trust (Exact name of registrant as specified in its charter) New York (governing law of 333-106982-19 Pooling and Servicing Agreement) (Commission 54-2150434 (State or other File Number) 54-2150433 jurisdiction IRS EIN of Incorporation) c/o Wells Fargo Bank, N.A. 9062 Old Annapolis Road Columbia, MD 21045 (Address of principal executive offices) (Zip Code) Registrant's telephone number, including area code: (410) 884-2000 (Former name or former address, if changed since last report) ITEM 5. Other Events On July 26, 2004 a distribution was made to holders of MASTR ASSET BACKED SECURITIES TRUST, Mortgage Pass-Through Certificates, Series 2004-OPT1 Trust. ITEM 7. Financial Statements and Exhibits (c) Exhibits furnished in accordance with Item 601(a) of Regulation S-K Exhibit Number Description EX-99.1 Monthly report distributed to holders of Mortgage Pass-Through Certificates, Series 2004-OPT1 Trust, relating to the July 26, 2004 distribution. 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 hereunto duly authorized. MASTR ASSET BACKED SECURITIES TRUST Mortgage Pass-Through Certificates, Series 2004-OPT1 Trust By: Wells Fargo Bank, N.A. as Trustee By: /s/ Beth Belfield as Assistant Vice President By: Beth Belfield as Assistant Vice President Date: 7/30/04 INDEX TO EXHIBITS Exhibit Number Description EX-99.1 Monthly report distributed to holders of Mortgage Pass-Through Certificates, Series 2004-OPT1 Trust, relating to the July 26, 2004 distribution. EX-99.1

~~Delaware~~MASTR ~~333~~Asset Backed Securitizations Mortgage Pass-~~106982~~Through 06Certificates Record Date: 6/30/04 Distribution Date: 7/26/04 MABS Series: 2004-~~1204982~~OPT1 Contact: Customer Service - CTSLink Wells Fargo Bank, N.A. Securities Administration Services 7485 New Horizon Way Frederick, MD 21703 Telephone: (301) 815-6600 Fax: (301) 815-6660 Certificateholder Distribution Summary Certificate Certificate Beginning Class Pass-Through Certificate Interest Principal Class CUSIP Description Rate Balance Distribution Distribution A-1 57643LCE4 SEN 1.58000% 221,394,345.85 301,219.31 9,471,387.81 A-2 57643LCF1 SEN 1.58000% 119,676,993.05 162,827.19 4,817,220.82 A-3 57643LCG9 SEN 1.56000% 168,352,861.49 226,154.01 5,623,659.91 M-1 57643LCH7 MEZ 1.82000% 42,151,000.00 66,059.98 0.00 M-2 57643LCJ3 MEZ 2.40000% 34,333,000.00 70,954.87 0.00 M-3 57643LCK0 MEZ 2.60000% 10,538,000.00 23,593.41 0.00 M-4 57643LCL8 MEZ 2.85000% 8,158,000.00 20,021.09 0.00 M-~~-------------------~~5 57643LCM6 MEZ 3.00000% 8,838,000.00 22,831.50 0.00 M-~~----------~~6 57643LCN4 MEZ 4.05000% 6,799,000.00 23,711.51 0.00 M-~~---------------~~7 ~~(State~~57643LCP9 orMEZ ~~Other~~5.05000% ~~Jurisdiction~~7,138,000.00 of31,040.39 ~~(Commission~~0.00 (ICE MAB4OPT1C OC 0.R00000% 7,818,296.S32 2,845,294.31 ~~Employer~~0.00 ~~Incorporation)~~R ~~File~~MAB4OP1R2 ~~Number)~~RES ~~Identification~~0.00000% ~~Number)~~0.00 ~~1285~~0.00 ~~Avenue~~0.00 ofP ~~the~~MAB4OPT1P ~~Americas~~Pre-pay ~~New~~0.00000% ~~York~~100.00 309,299.47 ~~New~~0.00 ~~York~~Totals ~~10019~~635,197,596.71 ~~------------------~~4,103,007.04 ~~-----~~19,912,268.54

~~SEQUENTIALLY~~Certificateholder ~~EXHIBIT~~Distribution NOSummary (continued) Current Ending Cumulative Realized Certificate Total Realized Class Loss Balance Distribution Losses A-1 0.00 ~~DESCRIPTION~~211,922,958.04 ~~NUMBERED~~9,772,607.12 ~~PAGE~~0.00 A-2 0.00 114,859,772.23 4,980,048.01 0.00 A-~~---------~~3 0.00 162,729,201.58 5,849,813.92 0.00 M-~~----------~~1 0.00 42,151,000.00 66,059.98 0.00 M-~~------------~~2 40.100 ~~Pooling~~34,333,000.00 ~~and~~70,954.87 ~~Servicing~~0.00 ~~Agreement~~M-3 0.00 10,538,000.00 ~~dated~~23,593.41 as0.00 ofM-4 ~~March~~0.00 78,158,000.00 120,021.09 ~~2004~~0.00 M-5 0.00 8,838,000.00 by22,831.50 ~~and~~0.00 ~~among~~M-6 ~~Mortgage~~0.00 ~~Asset~~6,799,000.00 ~~Securitization~~23,711.51 ~~Transactions~~0.00 M-7 0.00 7,138,000.00 ~~Inc~~31,040.39 as0.00 ~~depositor~~CE ~~(the~~0.00 ~~"Depositor")~~7,818,296.32 ~~Option~~2,845,294.31 ~~One~~0.00 ~~Mortgage~~R ~~Corporation~~0.00 as0.00 ~~master~~0.00 ~~servicer~~0.00 ~~(the~~P ~~"Master~~0.00 ~~Servicer")~~100.00 ~~and~~309,299.47 ~~Wells~~0.00 ~~Fargo~~Totals ~~Bank~~0.00 615,285,328.17 N24,015,275.A58 0.00 asAll ~~trustee~~distributions (required by the ~~"Trustee"),~~Pooling ~~relating~~and toServicing Agreement have been calculated by the ~~Series~~Certificate ~~2004-~~Administrator ~~OPT1~~on ~~Certificates~~behalf of the Trustee.

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