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 for a mortgage verifies the source of a homebuyer's gifted down payment funds.A gift letter is proof to the lender that the funds were gifted to a homebuyer for their home purchase, and not a loan or borrowed money. A down payment can be hard to come by. One option is to be gifted the money, but this has certain requirements, such as a gift letter. To use gift funds, you must provide a gift letter proving the money is not a loan. To use gift funds, you must provide a gift letter proving the money is not a loan. A gift letter for a mortgage shows your lender that you don't need to repay gift money toward your down payment. 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. A gift letter is one of the most important legal documents to prove the asset is yours.