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 statement that assures your lender the money that came into your account is a gift and not a loan.A short letter like this sample gift letter will cover all of the requirements your lender needs. 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. A mortgage gift letter is a document that helps satisfy the requirement that a borrower's down payment funds come from legitimate sources. A gift letter is a note from a donor to your lender regarding cash funds for your mortgage down payment.