Unclaimed income tax refunds worth more than $1.3 billion await an estimated 1.3 million taxpayers who did not file a 2017 Form 1040 federal income tax return, according to the Internal Revenue Service.

“The IRS wants to help taxpayers who are due refunds but haven’t filed their 2017 tax returns yet,” said IRS Commissioner Chuck Rettig. “Time is quickly running out for these taxpayers. There’s only a three-year window to claim these refunds, and the window closes on May 17. We want to help people get these refunds, but they will need to quickly file a 2017 tax return.”

The IRS estimates the midpoint for the potential refunds for 2017 to be $865 — that is, half of the refunds are more than $865 and half are less.