A gift letter is a piece of legal, written correspondence explicitly stating that money received isn't expected to be repaid. 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.The IRS will know of your gift. The general rule is that any gift is a taxable gift. However, there are many exceptions to this rule. In the US, gifts are always non-taxable. It should not be reported on the recipient's taxes. 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. The donor should complete the form in full and declare a fair market value for their tax deduction purposes. A gift letter is a piece of legal, written correspondence explicitly stating that money received from a friend or relative is a gift.