IRS Guides
P1771 – Charitable Contributions: Substantiation and Disclosure Requirements
P3833 – Disaster Relief: Providing Assistance Through Charitable Organizations
P4220 – Applying for 501(c)(3) Tax-Exempt Status
P4221pf – Compliance Guide for 501(c)(3) Private Foundations
P526 – Charitable Contributions: For use in preparing 2018 Returns