Had a long-running (auditor was hospitalized and replaced with someone in another city) Schedule C audit that client finally accepted IRS results. He'd had years of losses, and the IRS ruled "hobby." They wanted to see everything: receipts, canceled checks, where his money came from to pump into this activity running at a loss (inherited his father's investment account, so asked for statements), etc.; however, it was clear they really had made up their mind that it was a hobby and what direction they were heading from the beginning. They asked for written rebuttal on the nine points of business vs. hobby. We spent most of our time on that, writing and researching and applying to his business. I've heard from others that Schedules C, E, and F are the IRS's focus lately.