This guide offers tips for writing acknowledgement letters to families for donations made in memory of a loved one. What do you need to include in your donation acknowledgment letter?Remember to include gift details, such as gift date and gift amount, in your acknowledgment letter to the donor. 3. A donation acknowledgment letter (sometimes called a donation receipt or thankyou letter) is an email or paper that recognizes a charitable contribution. There is no set deadline when it comes to sending out thank you cards, though getting them out within two to three weeks after the funeral is ideal.