What is correspondence audit? It is where the IRS sends you correspondence in the mail, and they ask for more information about your tax return. Specifically, they might say, “you filed fifteen thousand dollars worth of charitable deductions, where is your proof of that?” Or there may be more specific questions in addition to that. Immediately you'll want to get together all of the documentation requested and return it to the IRS so that they can verify the deductions. If you're unable to do so they will almost certainly disallow the deductions.