What do you need to include in your donation acknowledgment letter? A gift acknowledgment letter weaves together your nonprofit's appreciation, engagement, and compliance efforts following a donor's generosity.Include the nonprofit's EIN so the the donor can to check the charity's tax-exempt status with the IRS. Gift acknowledgement letters are important for two reasons. First, they provide proof so donors can claim a US tax exemption. First paragraph: Immediately thank donors for their gift.