To complete your letter, have someone on your fundraising or leadership team sign off. Express your gratitude for the recipient's future support.I certify that the following person(s) personally appeared before me this day, each acknowledging to me that he or she signed the foregoing document:. A gift acknowledgment letter recognizes donors and can be used to claim tax deductions. You can begin the letter in a friendly and welcoming manner. I,. , have agreed to sponsor. Use the sponsor's name. Since sponsorship is all about building relationships, writing "To Whom This May Concern" just won't cut it.