Please verify that TurboTax looks at the total yearly tax due and divides it by 4 to arrive at a uniform quarterly tax due and compares it to the total yearly tax paid (withheld plus estimated) divided by 4. And then these two are compared to see if on a quarterly basis any amount is under-paid? I ask because I have a one-time Required Minimum Distribution (RMD) whose withholding would exceed the averaged quarterly tax due in the month it is done in, but then potentially show underpayment in the other quarters. My question is: If this is true, would TurboTax "pass" the underpayment test in remaining quarters if I did excess RMD withholding in the first quarter to "carry over" to the remaining quarters, given the total for the year is correct? The alternative would be to do normal withholding (no excess) for the RMD, then do estimated payments for the other three quarters such than no quarter is underpaid.
