The IRS says thatover $1.3 billion in 2017 tax refunds is still up for grabsmoney that belongs to an estimated 1.3 million people who have yet to file their tax returns for that year.

However, if youre owed money, youll have to move fasttheres only one week left to claim it, as the IRS will stop holding on to unclaimed 2017 refunds after May 17.

Claim it or lose it

By law, the IRS is required to hold on to unclaimed tax refunds for three years, after which that money becomes the property of the U.S. Treasury.

The IRS says that the average claim is worth around $865, but credits can be worth thousands of dollars, too.

Per CNBC, one of the credits up for grabs is the Earned Income Tax credit; its worth $6,318, and can be claimed by those with up to a maximum of $48,340 in income if you have three children (there are lower thresholds if you have fewer or no children, as listedhere).

Other credits can be claimed as well:

Additional Child Tax Credit

Adoption Credit

American Opportunity Credit

Refundable Credit For Prior Year Minimum Tax

Health Coverage Tax Credit

Credit for Federal Tax on Fuels

How to know if youre owed money

According to the IRS, the only way to know if the IRS is holding your 2017 refund is to file a return for that year (dont bother calling the IRS or using theWheres My Refund toolto find out, as it wont give you any tax refund information for 2017).

If youre not sure about filing but think you might be owed a refund, youmightwant to consult with a tax professional first, just to see if you qualify for any stray tax credits (some of which expired after 2017) as well.

How to file a 2017 tax return

You will need to file your 2017 taxes using the2017 tax form, eitheronlineor through the mail (see to it its postmarked by May 17)that years 1040s, 1040-As and 1040-EZs can befound on IRS.gov.

If you use commercial tax software like TurboTax or H&R Block, you will have either the option to use the original 2017 form in their current software, or to download the version of the tax software for the previous three years (2019, 2018, and 2017).

And if youre missing W-2, 1098, 1099, or 5498 forms from 2017, you’ve got the option to request them from former employers and banks, or from the the IRSGet Transcript Onlinetool.

Also, note that even if you qualify for a refund, that doesnt mean youll necessarily get a checkthose fundscouldbe applied to other debts that you might owe, like child support or other back taxes.