Minimize underpayment penalty

[jtp84]

I just did a preliminary tax analysis for 2019 and came to the conclusion that I did not withhold enough in my wages and will trigger an underpayment penalty. Will TurboTax help me do the quarterly payment for the 4th quarter which I believe is due on Jan 15, 2020? This would be to minimize the penalty that I will likely owe. 

Also, I keep reading that the IRS will calculate the penalty for you, but if there is an interest rate compounding daily and the IRS takes several more weeks/months to send me the penalty amount, that does not seem like a good situation to wait for. If I understand it correctly, the interest for Q1-Q3 has already started and the penalty continues to grow until the penalty is paid in full. Do I understand this correctly? Wouldn't it make sense to pay Q4 amount now PLUS some amount that will stop the interest from compounding?

Thanks in advance.

[Critter]

Actually to calculate the 2019 4th quarter estimated payment you use the 2018 tax program ... at this late date you can enter what you can in the 2019 program and see what you still owe then send a payment by 1/15 for what you think you will owe based on that estimate.   Then when you file you can include that payment and fill in the form 2210-AI to mitigate the penalty. 

[Bsch4477]

Download this. The 4th quarter voucher is included. 

https://www.irs.gov/pub/irs-pdf/f1040es.pdf

[jtp84]

Thank you!

I've estimated what the quarterly payments should have been according to 2019 Form 1040-ES. It comes out to 1/4 of line 14a. 

Do you know what impact to the penalty interest it would be if my Jan 15 payment is:

A. 1/4 of line 14a

B. Total amount of 14a

C. Remaining estimated taxes owed from line 14b (greater than 14a)

I'm assuming the interest will still accrue until all taxes owed are paid off and therefore option C from above should be paid to stop the interest from accruing?

[Critter]

Since you are only computing the last payment ( and the 2019 tax program will tell you what you expect to owe after all payments) you should pay all that you expect to owe now and not wait until you file by using option C. Any other option is not wise if you want to pay the least amount of penalties and interest.