According to the Internal Revenue Service (IRS) – the U.S. government agency that handles federal tax returns –  taxpayers are allowed three years from the original tax return due date to amend a return for either a credit or refund. In turn, the IRS has the same period of three years to audit a return and assess any additional tax.

The IRS Web site at www.irs.gov lists a few exceptions to the three-year rule. If you failed to report income that equals more than 25 percent of your gross income, you should keep your records for six years, as the IRS has six years to challenge returns with underreported income. Also, if you filed a loss due to bad debt or securities, keep your records for seven years. And if you may have filed a fraudulent return or did not file a return at all, you should keep your records for as long as you live.

If you are unsure if your return falls under the three-year rule then many experts advise keeping returns and corresponding records for seven years. Some even recommend keeping tax returns (not the records) indefinitely in the event the IRS or state tax agencies erroneously state that you did not file a return. Without documentation showing that the return was filed, it is more difficult to prove that the return had been submitted for the year in question.

State tax departments have varying recommendations for how long you should keep your state tax returns. For example, New York State recommends seven years and California recommends four years. To find out the rules in your state, call your state’s tax department or visit its respective Web site.