by default IRS assumes your income and withholding are even thru the year by quarter, but estimated taxes apply to specific quarters, so you can meet the safe harbor in total but if it wasn't paid evenly thru the year and you had an increase late in the year to make the safe harbor, you will be assessed an underpayment penalty for the earlier quarters.
you can reduce or potentially eliminate the penalty if you adopt the Annualized Income method on Form 2210 under Other Tax Situations / Underpayment Penalty section, to show you had uneven income to line up with the uneven estimated taxes. You have to calculate a quarterly AGI/withholding/LTCG yourself, it's a lot of extra work, I'd just pay the $50 to avoid the AI form and call this a win, but up to you.
if you are on desktop you can see Form 2210 and the penalty calculation in Forms mode it may not be on your forms list by default unless you adopt an exception method but do Open File and put 2210 in the search, or on Form 1040 you can double click thru Line 38 and again on the worksheet to bring it up. Not sure with TT Online but I assume it's in the PDF with all forms and worksheets.
