I know it is acceptable to deduct an over-payment of last year's Federal taxes from the first estimated tax payment of the current year. I would be making the first 2021 estimated payment on April 15, 2021 as required. My only uncertainty is whether this can be done if I file my 2020 taxes-- as allowed-- on May 17 of this year. I would probably add a bit to that payment to allow for any minor corrections made on the 1040 forms. I
