Can i file a 2020 return i didnt use for 2021?

[xmasbaby0]

Do you mean you have some 2020 income you did not put on a 2020 tax return?  NO you cannot put it on a 2021 tax return.    If you did not file a 2020 tax return then you can still do that but you need to use the correct 2020 software and 2020 tax forms.    Or if you filed a 2020 return and forgot to enter something, you will need to amend the 2020 return you filed to add that income.

Provide some details so we can help.

[TomK100]

Do you mean a W-2 from 2020?  Then, No.  You must file a W-2 from 2020 on a 2020  return.  Similarly, you enter 2021 W-2 information on your 2021 tax return.

Please see this helpful TurboTax FAQ on how to file prior-year tax returns: How do I prepare a 2020, 2019, or 2018 tax return?