Social Security Number or Individual Taxpayer ID Number (last 4 digits). Enter the entity name and identifying number from the tax return where the noncash charitable contribution was originally reported, if different from above.Download forms for Charitable Solicitation Registration, Charitable Trust Registration, and Professional Fund-Raiser Registration. Within the letter, please be sure to include the event date, your 501C tax id number, as well as the mailing address for the requester. Catholic Charities' tax identification number is 41-0721636.