As a general rule, you must pay estimated taxes in 2012 if both of these statements apply:

1) You expect to owe at least $1,000 in tax after subtracting your tax withholding (if you have any) and tax credits, and

2) You expect your withholding and credits to be less than the smaller of 90 percent of your 2012 taxes or 100 percent of the tax on your 2011 return.

For Sole Proprietors, Partners and S Corporation shareholders, you generally have to make estimated tax payments if you expect to owe $1,000 or more in tax when you file your return.

To figure your estimated tax, include your expected gross income, taxable income, taxes, deductions and credits for the year. Use the worksheet in IRS Form 1040-ES, Estimated Tax for Individuals. You want to be as accurate as possible to avoid penalties. Also, consider changes in your situation and recent tax law changes.

Estimated payments are generally due on April 15, June 15, Sept. 15 and Jan. 15 of the next or following year.

Special rules apply for farmers, fishermen, certain household employers and certain higher income taxpayers.

Also helpful is IRS Publication 505, Tax Withholding and Estimated Tax