If you are self-employed, chances are you pay estimated taxes. With the final 2008 payment due Jan. 15, it's worth considering how well your estimates match what you actually owe for last year -- and potentially adjusting that last payment as a result.
Here's what you need to know: Estimated taxes serve the same purpose as money withheld from a paycheck -- they fulfill your obligation to pay income tax. Most self-employed taxpayers pay their taxes in four equal payments, usually based on your tax liability for the previous year.
If your 2008 income varies significantly from what you earned in 2007, however, your estimated payments could be off. And that's no good. If you've overpaid your taxes, you've given Uncle Sam an interest-free loan on cash that could have been gathering interest for you in a savings account, essentially earning money for you.
If you've underpaid, the consequences could be worse: The IRS can sock you with a penalty for underpaying -- including a 7% penalty on the amount you failed to pay, possibly dating back to the April 15, 2008, payment. (As long as you pay 100% of your previous year's tax liability or 90% of the current year's liability, you won't incur this penalty.)