You fill in a reasonable, fair-market value of the donation. We've created this stepbystep guide on everything you need to know about creating a donation receipt letter for tax purposes.A donation receipt documents the details of a cash or property donation that's gifted to an individual cause or organization. Materials donated to Goodwill are tax deductible. Please retain this slip to serve as a receipt of your contributions. When making your donation, you will be required to fill out a form indicating what you are donating and the estimated value of your donation.