"If only the lower number of $113,328 is used, the penalty is even higher."

We're obviously looking at this differently, Bob. You don't need to describe it as not understanding the numbers. I look at the number to use for Safe Harbor that will prevent ever needing to compute a penalty or having Form 2210 in the first place. It's a different perspective.

"2024 Withholdings $113,328 + additional Medicare tax $3,944 = $117,172" it is $117,272.