There remain two other substantive errors on Form 2210 as of 2/26/2021:
1. The tax computations on schedule AI, line 14 column (a), (b), and (c) are incorrect if you have qualified dividends. Specifically, on my return Turbotax is incorrectly applying exactly a -12% tax rate to my qualified dividends when it should be a +15% tax rate. This error results in estimated quarterly taxes that are lower than they should be by 27% of qualified dividend income.
2. IRS instructions for Form 2210, Line 11 state "Any overpayment from your 2020 return applies to your 2021 estimated tax payments. Generally, treat the payment as made on April 15, 2021." Instead Turbotax incorrectly fails to apply the prior year refund to any quarter in Form 2210.
