A nonrefundable individual tax credit for voluntary cash contributions to a qualifying charitable organization (QCO). Please send this completed form with payment to: Arizona Tax Credit.MAIL: P.O. Box 1172, Higley, AZ 85236 FAX: 877.750.7050. Your gift may qualify for the Arizona Tax Credit for Qualifying Charitable Organizations. Our AZ Tax Credit ID Number is: 21020. Easy online donation form submission for tax credit. Fill out the required details for tax year qualification. Many online tax platforms also allow you to complete AZ Form 321 digitally! You can visit the Arizona Department of Revenue for more information. The letter will serve as proof of payment for your tax records.