After you file

From the IRS website as of today, 02/27/2021:

 

"E-filing is available for amending 2019 and 2020 returns that were originally e-filed. E-filing amended returns will result in much faster processing and refunds." " Contact your tax professional or preferred tax software provider to verify their participation in amended return e-filing, for specific instructions needed to submit an amended return, and for answers to any questions. An amended return for tax year 2019 or 2020 can also be filed on paper.  As of February 2021, the most recent paper Form 1040-X is the January 2020 revision.  If you are amending your 2020 calendar year return, you should manually enter “2020” in the entry box next to “calendar year” on the line below the calendar year checkboxes. You should then complete the form as usual, using the most recent revision of Form 1040-X and the Instructions for Form 1040 for the tax year being amended."