Mistakes on tax returns aren’t at all unusual. Even tax preparers frequently goof. A 2012 article in the Morning Call newspaper notes that treasury inspector general for tax administration found that as many as three out of five prepared returns may have problems. If you find something wrong on your tax return, you can fix it, although you are liable for any extra taxes due and you might have to ante up a late payment penalty. The good news is that fixing tax return errors is pretty straightforward.

What Mistakes to Fix

When you do your taxes, you might forget to include some income, overlook a deduction or miss claiming a tax credit. These types of mistakes are likely to change the amount of tax you thought you owed Uncle Sam. This means you either owe the Internal Revenue Service more money or you are entitled to a bigger refund. You’ll need to file an amended return to fix these problems. Not every tax return mistake requires amending, however. If you simply got the math wrong or forgot to attach a schedule or form, the IRS says not to submit an amended return. The IRS computers correct mathematical errors. There may be no need to provide a missing form. If any action is required, the IRS will notify you.

When to Amend

If you find something wrong with your tax return and it means you owe more, the IRS says to file an amended return and pay as soon as you can to keep penalties to a minimum. You might find that amending will get you some money back instead. If so, and you are waiting on a refund based on the original return, hold off submitting the amended return until the refund check arrives. Don’t put off filing an amended return for a refund too long, though. You can only amend to get a refund for three years after the original due date of your tax return.

Procedure for Amending

You don’t use the same form for an amended return that you used when you originally filed. Instead of a 1040, 1040A or 1040EZ, use IRS form 1040X, “Amended U.S. Individual Tax Return.” If additional forms or schedules have to be revised, attach corrected versions to the 1040X. When you are amending because you owe additional taxes, send payment with the amended return.

Tax Preparer Mistakes

You might have your tax return prepared by a certified public accountant or other professional. If there’s something wrong with the return, you are still responsible for any additional taxes and penalties. Tax preparers often will pay penalties that result from a mistake they made, although they won’t pay any additional taxes. Assuming responsibility for penalties on the part of tax preparers isn’t automatic. Before you choose a tax preparer, find out what the policy is.