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 document stating that any money received from family or friends is a cash gift and not a loan.They insist on us signing a 'gift letter' to certify that the funds from my parents are not debt financing and that we will not owe interest payments to them. 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. If your father intended for the money to be a gift, and the letter supports that characterization, you have no obligation to pay her back. You need to provide any and all documents affirming that the money is indeed a gift not a loan from your parents.