What we found was that the solution was more complex than we had originally considered. In our case, changing our filing status from MFJ in 2019 to MFS in 2020 required additional calculations (done by hand) on both of our separate 2020 tax returns. This information does not appear to be calculated automatically by TurboTax.
The “About” instructions that TurboTax provides for Line 8 on Form 2210 helped us through this process --> “If you are not filing a joint return for 2020, but filed a joint return for 2019, figure the tax both you and your spouse would have paid if you had filed separate returns for 2019. Then multiply the joint tax liability by your separate tax liability divided by the sum of both spouses' separate tax liabilities. [TurboTax, Form 2210, “About Line 8.”] To complete this task, we then had to update the Federal Carryover Worksheet with this 2019 tax liability information on each of our MFS 2020 tax returns.
Following those instructions we were then able to successfully complete Form 2210; that resolved our issue. (As it turned out we had no tax penalty.)
