Why wasn't my estimated tax penalty calculated?

[ANH11]

I received a CP14 for underpayment + interest. I filed my extension on time, and made a large estimated tax payment. Early Oct. when I finished inputting all my numbers, I still owed another 24% of my total taxes, so I filed & paid the remaining 24%. Since TT knew I filed the extension, then told me I still owed another 24%, why did it not include an estimated penalty on the outstanding 24% I had to pay?  I would have loved to pay that last month vs now.  I even remember TT asking, when you do you expect to pay the outstanding balance and I would put the same day down, but hello, that 24% is already 5 months late...

[VolvoGirl]

Did your payment with Extension show up on schedule 3 line 10 and goes to 1040 line 31?  Did Turbo Tax calculate any penalty on 1040 line 38?    Turbo Tax only calculates an estimated penalty amount.   Even if Turbo Tax entered a penalty on line 38, it's common and normal and expected for the IRS or state to bill you for more or send you a refund.  They don't know for sure when the IRS will get your tax due payment.  

[ANH11]

Thank you, yes, my extension & payment is on schedule 3 line 10, and is shown on 1040 line 31, 1040 line 38 is blank :(

Understandably the estimated penalty that should have appeared on line 38 would have only been an estimate, but it would have been hell of a lot closer to the actual number than $0. This seems like a bug in the software, yet, this is something so simple to catch. If payer has extension AND taxes owed > taxed paid, calculate the interest owed. I'm just baffled I'm getting pinged to pay what is now an additional 1 month of interest.

[Mike9241]

it seems what you are saying is that you had a late payment penalty which Turbotax does not compute nor does it computer interest on such late payment. A late payment penalty (owing a balance not paid by the due date of the return)  is different than an underpayment of estimated tax penalty (not having enough withholding and timely estimated tax payments to cover the minimum required. Turbotax does compute this unless the taxpayer checks a box asking the program not to)