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

There is no penalty for failure to file, if you are due a refund. But, if you wait to file a return or otherwise claim a refund, you risk losing a refund altogether. An original return claiming a refund must be filed within three years of its due date for a refund to be allowed in most instances.

After the expiration of the three-year window, the refund statute prevents the issuance of a refund check and the application of 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.