A taxpayer who received a CP-48 notice indicating that their existing ITIN has expired should have: Applied for a new ITIN when they filed their 2021 federal tax return in 2022. Applied for a new ITIN on or before December 31, 2021. Renewed their existing ITIN as soon as possible, but only if they intend to file a U.S. tax return or claim for refund in 2022. Renewed their existing ITIN as soon as possible, regardless of their intent to file a U.S. tax return or claim for refund in 2022. Mark for follow up