Up to one million people a year may lose out on a tax refund simply because they did not file a federal income tax return.

Many taxpayers may not file because they didn’t earn enough money to be required to do. However, taxpayers who had federal taxes withheld by their employer may be eligible for a refund of those taxes. Also, even if you aren’t required to file, you may qualify for benefits like the Earned Income Tax Credit.

You must file a tax return to get the money.

There is usually no penalty for failure to file, if you are due a refund. But, if you wait too long to file a return or otherwise claim a refund, you risk losing your refund altogether.

In most cases, an original return claiming a refund must be filed within three years of its due date for the IRS to issue a refund.

Generally, after the three-year window closes, the IRS can neither send a refund for the specific tax year. nor apply any credits, including overpayments of estimated or withholding taxes, to other tax years that are underpaid.

Current and prior year tax forms and instructions are available on the IRS.gov Forms and Publications page.

Taxpayers who are missing Forms W-2, 1098, 1099 or 5498 should request copies from their employer, bank or other payer.

Taxpayers who are unable to get missing forms from their employer or other payer should go to IRS.gov and use the Get a Transcript tool to order a “Wage and Income transcript.” Taxpayers can also file Form 4506-T to request a transcript of their tax return. Taxpayers can use the information on the transcript to file their return.