8-K/A 1 csf03021_sep.txt SEP 8K-A UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington D. C. 20549 Form 8-K/A Current Report Pursuant to Section 13 or 15(d) of The Securities Exchange Act of 1934 Date of Report (Date of earliest event reported): September 25, 2003 CREDIT SUISSE FIRST BOSTON MORTGAGE SECURITIES CORPORATION Mortgage Backed Pass-Through Certificates, Series 2003-21 Trust (Exact name of registrant as specified in its charter) New York (governing law of 333-107055-03 54-2123768 Pooling and Servicing Agreement) (Commission 54-2123765 (State or other File Number) 54-2123767 jurisdiction 54-2123766 of Incorporation) IRS EIN c/o Wells Fargo Bank Minnesota, 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 Subsequent to filing the 8-K relating to the payment date on September 25, 2003, a revision was made to the CREDIT SUISSE FIRST BOSTON MORTGAGE SECURITIES CORPORATION, Mortgage Backed Pass-Through Certificates, Series 2003-21 which was not included in the original 8-K filed. This revision was not previously disclosed in a 1934 Act filing. An amended 8-K will be filed. The revised data has been and will continue to be available on the Wells Fargo Bank, Minnesota, as Trust Administrator, website at www.ctslink.com. 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 Amended monthly report distributed to holders of Mortgage Backed Pass-Through Certificates, Series 2003-21 Trust, relating to the September 25, 2003 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. CREDIT SUISSE FIRST BOSTON MORTGAGE SECURITIES CORPORATION Mortgage Backed Pass-Through Certificates, Series 2003-21 Trust By: Wells Fargo Bank Minnesota, N.A. as Trust Administrator By: /s/ Beth Belfield, Assistant Vice President By: Beth Belfield, Assistant Vice President Date: 11/14/03 INDEX TO EXHIBITS Exhibit Number Description EX-99.1 Amended monthly report distributed to holders of Mortgage Backed Pass-Through Certificates, Series 2003-21 Trust, relating to the September 25, 2003 distribution. EX-99.1

Delinquency Status By Groups

CSFB MORTGAGE BACKED PASS THR CERTS SER 2003-21 8-K/A