Fees, at least from the school, should be on an invoice. My experience is that most textbooks these days are purchased or rented through online transactions - that should be an easy receipt to find and keep. Anything after that, if you tell your kid multiple times that certain receipts need to be retained and the message doesn't sink in... well, sorry. You'll probably never hear from the IRS, but my concern at that point would be simply having documentation so that I can pull the correct amount from the 529.