If you applied your 2020 tax refund to your 2021 return, that will automatically be applied as a first-quarter estimated payment.
You can then use the annualized method to calculate your underpayment penalty if any. Since a good chunk of your income was earned in the last quarter due to the conversion, this may lower or eliminate your penalty. Even if you don't need to pay a penalty, you will need to include Form 2210 with your return if you otherwise would have had to pay it.
- Go to Federal > Other Tax Situations > Additional Tax Payments > Underpayment Penalties and click Start/Revisit.
- Enter your prior-year information to see if you qualify for the safe harbor rule.
- In the Annualized Income Method screen, select Yes.
- Enter your quarterly income and credits by quarter. TurboTax will recalculate your underpayment penalty using the annualized method and if it yields a better result, will allow you to use this method.
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