Thanks, @dr3412 that's good to know that your return was not rejected. Gives me hope that mine won't. I want to avoid paper filing as the IRS is understaffed and more human processing of a paper return probably drives up the chances of an error occurring. This, after I have painstakingly gathered my data, entered it and reviewed it multiple times seems counterproductive.
There is a strange hint that TT is looking at the 2020 overpayment (refund applied to 1st quarter of 2021). The Underpayment Penalty Worksheet which you can see by doing a Quick Zoom of Line 19 Penalty on Form 2210, has a couple entries (in my case) that are the correct overpayment (instead of underpayment) for the payment dates, 4/15 and 6/15. It could have only arrived at these figures by using the long lamented seemingly ignored 2020 overpayment. But the sheet still conflictingly says in its top line summary for the payment dates that I have an underpayment, though it doesn't go through the penalty calculation.
