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. We'll also show you how to write a gift letter with a gift letter template so you can help your donor prepare for underwriting.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. What is included in a gift letter? A gift letter is a note from a donor to your lender regarding cash funds for your mortgage down payment. A gift letter is an important, formal, legal piece of documentation that can help explain that a (usually rather large) sum of money was gifted to you. This guide explains how to document gift funds for a mortgage and meet lender requirements.