Thanks, but I'm wondering how to reconcile your answer with the IRS' own web site which I quoted in my question. In fact TurboTax's own help says that paying 100% of your tax bill from last year throughout the next one is called a "safe harbor" option. Well, I did that. 100% (and more) of my 2020 tax bill was withheld from my paycheck during 2021. So, both TurboTax and IRS says I should be safe, yet TurboTax applied a penalty anyway. Why?
