@Marx - they have the right to audit and ask for the documentation; beyond that, read the statement at the bottom of your tax return, just above your signature:
"Under penalties of perjury, I declare that I have examined this return and accompanying schedules and statements, and to the best of my knowledge and belief, they are true, correct, and complete.
This is how they 'getcha' if there is an audit and you can't prove what you did.
