One of the biggest hurdles you'll face in running your own business is to stay on top of your numerous obligations to federal, state, and local tax agencies. A tax headache is only one mistake away, be it a missed payment or filing deadline, an improperly claimed deduction, or incomplete records. And, you can safely assume that a tax auditor presenting an assessment of additional taxes, penalties, and interest will not look kindly on an "I didn't know I was required to do that" claim. The old legal saying that "ignorance of the law is no excuse" is perhaps most often applied in tax settings.