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I agree that the way 2210 reads that line 6 defines the safe harbor cut off.  But something more is happening in the background that seems to override the first pass underpayment claim.  I am in the 110% safe harbor camp.  My W-2 withholding for 2023 was less than 50% of my estimated tax liability, so I made 4 quarterly payments to meet the 110% level.   Yet, even with this info TT showed I owed a penalty.  

But when I went to "Other Tax Situations" and opened the "Underpayment penalties", I was able to answer a couple of questions and then enter my 2022 tax liability.  This is the info that I was very surprised (and disappointed) that TT didn't already import nor did ask for this information before declaring I owed a penalty.

After I did this TT then said I owe no penalty.