An estimated 1.5 million taxpayers who did not file a 2018 Form 1040 federal income tax return may be owed about $1.5 billion in unclaimed income tax refunds, but they must act by the April tax deadline, according to the Internal Revenue Service. There’s just a three-year window to seek these returns under the law, which ends with the April tax deadline this year.

The IRS forecasts that the midpoint for potential refunds in 2018 will be $813, meaning that half of the refunds will be more than $813 and half would be less.

Most individuals have a three-year window to seek a tax refund if they have not filed a federal income tax return. The money becomes the property of the US Treasury if they do not submit a tax return within three years. For most taxpayers, the time for filing 2018 tax returns concludes on April 18, 2022. Maine and Massachusetts residents have until April 19, 2022 to file their taxes. Taxpayers are required by law to properly address, mail, and postmark their tax returns by that date.

The IRS advises taxpayers seeking a 2018 tax refund that if they have not filed tax forms for 2019 and 2020, their refund checks may be held. In addition, the refund will be applied to any sums still outstanding to the IRS or a state tax agency, as well as unpaid child support or past due federal bills like student loans.

People risk losing more than just their refund of taxes withheld or paid in 2018 if they fail to file a tax return. The Earned Income Tax Credit may be available to many low and moderate-income workers (EITC). The credit was valued up to $6,431 in 2018.