8-K 1 mst03012_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 SECURITIZATION TRUST Mortgage Pass-Through Certificates, Series 2003-12 Trust (Exact name of registrant as specified in its charter) New York (governing law of 333-106982-10 54-2139230 Pooling and Servicing Agreement) (Commission 54-2139231 (State or other File Number) IRS EIN jurisdiction 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 SECURITIZATION TRUST, Mortgage Pass-Through Certificates, Series 2003-12 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 2003-12 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 SECURITIZATION TRUST Mortgage Pass-Through Certificates, Series 2003-12 Trust By: Wells Fargo Bank, N.A. as Master Servicer By: /s/ Beth Belfield as Assistant Vice President By: Beth Belfield as Assistant Vice President Date: 7/29/04 INDEX TO EXHIBITS Exhibit Number Description EX-99.1 Monthly report distributed to holders of Mortgage Pass-Through Certificates, Series 2003-12 Trust, relating to the July 26, 2004 distribution. EX-99.1

MORTGAGE ASSET SEC TRANS MORT PASS THR CERTS SER 2003-12 8-K