Stop! Don't mail in your income tax return yet. You can save yourself and the Internal Revenue Service a lot of trouble by checking to see if you committed any of the most frequent taxpayer errors.

To no one's surprise, the IRS is discovering that taxpayers are confused by the Tax Reform Act of 1986. Who's to blame? The Congress which passed the law, and others who defend it as a simplification. They ought to be sentenced to fill out tax returns of a few middle-income taxpayers.The most frequent taxpayers' errors are:

Claiming an exemption for yourself when you can also be claimed as a dependent by another taxpayer. This problem arises most frequently with students who work part-time. Before tax reform, both parent and child could claim the exemption. Now only the parent can. Additionally, these same dependents should check the box on their returns indicating they can be claimed as a dependent on someone else's return.

Deducting nothing for state and local income and real estate taxes. Taxpayers misread the note on Schedule A which tells them sales taxes can no longer be deducted. The IRS finds taxpayers don't understand that state and local income and property taxes are still deductible.

Claiming an extra exemption for being blind or over age 65. This is not allowed under the new law. Instead, these taxpayers get a larger standard deduction. Taxpayers who are blind or over 65 get no tax break, however, if they itemize deductions.

In the unlikely event you have a question about the brilliantly drafted tax law, call the toll-free tax information lines at the IRS: 1-800-424-1040, Monday through Saturday from 8 a.m. to 5 p.m.

Warning! The IRS will give you the wrong answer 39 percent of the time, according to the General Accounting Office. Moreover, you are responsible for paying the correct tax no matter what advice you get from the taxman.

THE MORAL: IRS gives free tax advice but you get what you pay for.

TRUE OR FALSE: April 15 is the deadline for filing your tax return and paying what you owe.

Answer: Not always.

If you can't file your return on time, you can get an automatic four-month extension, giving you until Aug. 15 to file. Just estimate the amount due, complete IRS Form 4868 and send it with your money to the IRS by April 15.

A few words of caution: If you pay less than the final tax you owe, you will be charged interest. If the tax paid is less than 90 percent of the amount due, you may also be subject to a late-payment penalty.

The IRS doesn't like to talk about it, but if you cannot pay, you don't have to on April 15 under certain circumstances.

Taxpayers who can prove a severe economic hardship can get a six-month payment extension. You must show you don't have cash or assets easily converted into cash sufficient to pay the amount due. You must also prove you can't get money by borrowing or selling assets other than at sacrifice prices.

The payment extension Form 1127 has to be filed with your return by April 15.

If you qualify for a hardship extension, you will avoid late penalties and property seizure. Interest will accumulate on the taxes owed.

THE MORAL: As much trouble as April 15 is, an extension merely postpones the inevitable.