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 gift letter is a note from a donor to your lender regarding cash funds for your mortgage down payment.The letter needs to indicate that the money is a gift and not actually a loan you must pay back. A gift letter for a mortgage shows your lender that you don't need to repay gift money toward your down payment. Pin down the specifics of the property in question. Clearly state the property's address, ensuring there's no ambiguity about where the gift funds are intended.