Was the 1099-R for tax year 2019? Then you must amend your 2019 tax return (and not 2020).
Please see this TurboTax article for instructions on how to amend your tax return in TurboTax.
Any changes in tax on your amended return would not affect your 2021 tax return. And you can continue to prepare and file your 2021 tax return.
I did amend the 2019 successfully. The amended return cause us to pay more taxes for both federal and state. Paying more taxes should affect the 2020 taxes.
Rich
Back taxes paid for year 2019 are not deductible and do not affect your 2020 tax return.
To follow-up on the comments from @MinhT1, the interest that you paid for failing to timely pay the tax when due is not a deductible expense on your 2020 return or your 2021 return. If you are owed a refund on your 2021 tax return, and you have not paid the late interest charges, then the IRS is likely to reduce your refund amount by the amount of the late interest charge.
Is this true in the state taxes as well.
Thank you in advance,
Poolguy51
If you are referring to state refund against state tax liabilities, yes, the same applies to your state tax refund. If you have an existing tax bill, the current year's refund will be partially or wholly applied to the tax liability first before it is issued to you, if any amount remains.