What do you need to include in your donation acknowledgment letter? A donation acknowledgment letter (sometimes called a donation receipt or thankyou letter) is an email or paper that recognizes a charitable contribution.A donor acknowledgement letter should include a few specific items to assist the donor and help your organization comply with IRS regulations. When you donate stock to the Charlotte Mecklenburg Library Foundation, you may realize tax benefits, which result in a larger gift at a lower cost to you. 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.