What do you need to include in your donation acknowledgment letter? Include the nonprofit's EIN so the the donor can to check the charity's tax-exempt status with the IRS.Want to learn how to write and structure donor acknowledgment letters? Check out these tips and sample letters to make a greater impact. First, there is the in-kind donation request sent to a potential donor. Final paragraph: Thank your donor again and outline how their donation was used to further your purpose. Learn more about how to write meaningful acknowledgement letters to families for donations made in memory of their loved ones with this comprehensive guide.