The IRS taxes gifts made over a certain dollar amount. A gift letter for a mortgage shows your lender that you don't need to repay gift money toward your down payment.A gift letter is a note from a donor to your lender regarding cash funds for your mortgage down payment. If you use gifted funds toward your home purchase, your mortgage lender will need a gift letter to explain that the money is not a loan. Recipients of cash gifts aren't taxed on the gift. Gift money for USDA loans can come from any donor who doesn't have an interest in the transaction. So, for example, giving an adult child money toward a down payment on a home would not change the taxable nature of the gift. Your bank needs a written letter to prove that any money gifted to you to help buy a house is in fact a gift, not a loan. 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.