The Internal Revenue Service (IRS) might have your money. The tax agency has announced that more than $1.4 billion in outstanding refunds remain unclaimed from 2015. Yes, billion. That represents more than one million taxpayers who might have qualified for a refund but who did not file a federal income tax return for 2015. If you are due a refund, you must file a federal income tax return to get your money. You typically have a three-year window following the return due date to claim your tax refund. To claim your refund for the 2015 tax year, your return must be postmarked on or before Tax Day, April 15, 2019 (except for taxpayers in Maine and Massachusetts, who have until April 17, 2019).