What do you need to include in your donation acknowledgment letter? What is required in a donation acknowledgement letter?A gift acknowledgment letter weaves together your nonprofit's appreciation, engagement, and compliance efforts following a donor's generosity. This receipt is issued to individuals who have donated cash or payment, personal property, or a vehicle and seek to claim the donation as a tax deduction. Want to learn how to write and structure donor acknowledgment letters? Check out these tips and sample letters to make a greater impact. There is no official IRS form that the exempt organization has to complete. When does the nonprofit need to send the written acknowledgment letter to donors? To do this, you must file Form 1023, Application for Recognition of Exemption Under Section 501(c)(3) of the Internal Revenue Code. Proof of charitable contributions refers to the substantiation that the Internal Revenue Service requires to claim a donation as a tax deduction.