@lnk-fr
https://www.irs.gov/filing/time-you-can-claim-a-credit-or-refund#:~:text=You%20can't%20get%20a,time%....
"When you didn't file a claim within the 3-year or 2-year expiration dates
You can't get a credit or refund if you don't file the claim within 3 years of filing your original return, or 2 years after paying the tax, whichever is later, unless you meet an exception that allows you more time to file a claim."
Agree with the IRS in writing to extend the time limit to assess tax: The time limit is specified in your agreement, plus 6 months, to claim a credit or refund.
