Follow the basic instructions on this sample letter to fill out the form, and be sure you understand the fine print. Then, provide the lender with the following documents: A marriage license or graduation certificate.A letter explaining the source of funds. Spouses may not file a joint gift tax return. Each individual is responsible to file a Form 709. Here's a sample gift letter you can use to prove that the money is truly meant as an outright gift, with no expectation of repayment. As noted earlier, your bank should provide a gift letter template for you to complete. A gift letter for a mortgage verifies the source of a homebuyer's gifted down payment funds. A couple meeting with a mortgage lender to submit a gift letter. This form is to be used for disclosing gift information.