You will need to complete the Declaration form. An affidavit of marriage is a legal document and a sworn statement submitted to the court or another institution, to verify that two people are married.1. Oath of Witness to tell the truth: 2. A Marriage Affidavit is a sworn statement affirming the date and validity of a marriage. Complete this online application (make sure to fill out all fields) and click the Finish button when done. 25 per page after 50 pages. Additional costs may be assessed upon processing a request. Check or money order made out to Salt Lake City Corporation. Bring the documents to the Salt Lake City Recorder's Office (451 South State Street, Room 415, Salt Lake City, UT) during your scheduled appointment. To obtain a marriage license, download and legibly complete all areas of the Marriage Application Form.