WASHINGTON – It’s a sinking feeling. You’ve done your taxes and they’re in the mail, and you realize you’ve made a mistake.

Take a deep breath. Experts say that tax code has become so complex those who make mistakes are in good company.

If the IRS owes you money, you can fix the problem by filing a 1040X form. Taxpayers have three to five years to do so. However, if you owe the IRS money, things become more complicated.

The longer you wait to correct the mistake, the higher the fees and penalties. Interest on the money owed accrues.

The best way to avoid problems is to check, and double check, your math before dropping the forms in the mail.

And don’t forget to sign.

The IRS has a video on how to file an amended return.

WTOP’s Del Walters contributed to this story. Follow WTOP on Twitter.

(Copyright 2012 by WTOP. All Rights Reserved.)