Did you use the Online browser version or the Desktop installed program? If you used the Desktop program you need to have the .tax2020 on your computer (or have a backup saved) and the 2020 program installed. If you deleted the .taxfile check your recycle bin or trash. And check on One Drive and any other drives or backup services you use.
To amend a return
Some quick ground rules:
You can correct a return that you've already filed and had accepted. Select the year that applies and use this guide to proceed.
Select your tax year for amending instructions:
For additional information please refer to How to Amend