Correctly calculating your estimated tax payments and/or withholding is even more important as the year end approaches. Accurate calculations are especially important as third and fourth quarter payments become due, and your income and expenses for the rest of the year can be more accurately projected.

Estimated tax payments
You are required to pay estimated tax if you receive income from which tax is not withheld, including income from self-employment, dividends and interest, capital gains and losses, rental income, and alimony, and your tax is expected to be $1,000 or more (after subtracting credits and withholding). Generally, individuals who do not pay at least 90 percent of their tax through withholding must estimate their income tax liability and make equal quarterly payments of the “required annual payment” liability throughout the year.

Higher-income taxpayers.
For higher-income taxpayers whose adjusted gross income (AGI) shown on the preceding year’s tax return exceeds $150,000 ($75,000 for married individuals filing separately), the required annual payment is the lesser of 90 percent of the tax for the current year, or 110 percent of the tax shown on the return for the preceding tax year.

Estimated tax payments are due quarterly. For most individuals, the due dates for the 2010 tax year are: April 15, June 15, and September 15 of 2010, and January 15, 2011. Failing to pay enough estimated tax on each installment date may result in a penalty for underpayment of estimated tax, even if you are due a refund. Therefore, properly calculating your payments is vital to avoid the penalties, including calculating adjustments needed in remaining quarters (including as soon as September 15, 2010 for the third quarter).

Third quarter payments are around the corner – September 15, 2010 – for the period June 1 through August 31. Fourth quarter payments will be due January 15, 2011 for the period September 1, 2010 through December 31, 2010. If your total estimated payments and withholding add up to less than 90 percent of what you owe, you may face an underpayment penalty.

With the third and fourth quarter payments becoming due, ensure you are properly withholding and paying enough in estimated tax. Look at your projected year-end tax payments as compared with your expected tax liability to determine if your estimated tax payments need some tweaking. If your payments are expected to be less than 90 percent of current-year tax, you will generally need to increase your withholding or make estimated tax payments.

You may want to file a new W-4 with your employer adjusting your withholding to withhold more from your final paychecks for the year if you are currently underwithholding. This will help avoid being subject to a penalty when you file your return.

Adjusting estimated tax payments
A change in your business’s income, deductions, credits, and exemptions may also make it necessary to refigure your estimated payments for the remainder of the year. To avoid either a penalty from the IRS or overpaying the IRS interest-free, consider increasing or decreasing the amount of your remaining estimated payments.

If, during the quarter, you learn that a change in your business’s anticipated income, deductions, credits, exemptions, or other adjustments will either increase or decrease your business’s tax liability, and therefore affecting your required annual payment for the remainder of the year, you should adjust your remaining quarterly payments accordingly.

Refiguring tax payments due
To change your estimated tax payments, refigure your total estimated payments due. Next, determine the payment due for each remaining payment period. Be careful when refiguring your remaining payments. The IRS may assess a penalty against you when filing your return at the end of the year if an estimated tax payment for a previous period is less than one-fourth of your amended estimated tax. So be cautious when refiguring any tax payments.