In December, one of your clients, Tim Huffman, donated a valuable piece of art to a local charity to be auctioned at its annual fundraising auction. When Mr. Huffman donated the art, it was appraised for $20,000. However, at the auction held on January 20, 2014, it sold for $35,000. Mr. Huffman claims that the appraisal was obviously wrong and that the value of what he donated was obviously $35,000. Consequently, he wants to deduct $35,000 on his tax return.

Discussing the tax implications of the appraisal and subsequent sale of the art he donated.

I'm having trouble finding the laws/rules about this.