Learn what an acknowledgement receipt is and how to create one for your business (with a template and two examples). How do you fill out an acknowledgment letter?Fill out, sign, and affix your official seal to the Notary certificate. The wording requirements for acknowledgment certificates vary from state to state. Learn how to draft a professional company acknowledgement letter with the help of this template. 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?