If you didn’t file a tax return amid the worst of the Covid-19 pandemic and believe you’re eligible for a refund, the Internal Revenue Service wants to hear from you.

The agency said this week that more than $1 billion in unclaimed refunds for tax filing year 2020 are sitting in its coffers, and that it’s still possible for eligible filers to claim.

Due to the pandemic, filers got an unusual extension on the regular three-year return-filing window. They now have until May 17, 2024 to claim their refund for tax year 2020.