Do I have to file my 2020 tax return prior to April 15 so that my 2020 estimated tax over payment can be applied to the 1st quarter 2021 estimated tax payment that is due by April 15th 2021?
how else would the IRS know that is your intent? they don't know that you are NOT going to ask for the refund.
each year's set of payments stands on their own, so unless you instruct the IRS to move the excess from 2020 over to 2021, that first payment due 2021 will look deficient.
The due date of your 2020 tax return has been extended to May 17, 2021.
If you had on your 2020 tax return a refund that you wish to be applied to next year's tax, that refund will still be applied to your first installment of 2021 estimated tax
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