In determining the beginning of the lookback period for refund claims for returns with due dates postponed by Notice 2021-21 or Notice 2020-23, the IRS will disregard the periods from April 15, 2020, to July 15, 2020, and from April 15, 2021, to May 17, 2021. This change will align the lookback periods with the postponed return filing due dates.