The letter must explain who is gifting the money, where the donor's funds are coming from and the relationship between the donor and the recipient. A mortgage gift letter is a document that helps satisfy the requirement that a borrower's down payment funds come from legitimate sources.This guide explains how to document gift funds for a mortgage and meet lender requirements. To use gift funds, you must provide a gift letter proving the money is not a loan. In the letter, the donors must specify that the money is a gift. Mortgage Gift letter is what the donor of the gift writes to the lender stating that he has offered a gift of money to the home buyer. That's why a gift letter is a requirement for gifted down payment funds. What are seasoned funds? Each detail included in the gift letter serves a specific purpose and helps the lender assess the legitimacy of the gifted funds. A gift letter for a mortgage shows your lender that you don't need to repay gift money toward your down payment.