Do you really want to go through the aggravation of an audit. They usually audit for 3 years. If they think fraud is involved they can go back much further. You have to produce all of your receipts , bookkeeping records, tax returns and possibly have your accountant present.

If the IRS finds itself devoting more than an alloted number of hours on an audit they are almost hell bent on finding an error in your return to bill you for justifying their time. I used to share an office with a tax attorney who was a former IRS revenue agent. He told nightmare stories about collecting and extracting revenue from tax payers.