Paying last year's estimated tax underpayment through tax returns?

[agriagro]

I am getting an underpayment penalty due to missing one of my estimate tax payments in 2021. As I'm going through this section on TurboTax it got to a part where it's asking to enter the "date you paid or will pay your balance due." Are we able to pay the tax I owe through TurboTax while filing my tax return, or do I still have to pay those estimated taxes separately to the IRS and include here the date I do that?

Also, would I still calculate how much I still need to pay based on the 1040-ES? Although I no longer technically need to "estimate" the tax as I now know exactly how much income I made.

Thank you!

[Spino]

You may have an underpayment all the same since the deadline for estimated tax in the fourth quarter was January 15. Estimated tax is due quarterly.

The date you pay the tax due is used to calculate interest due, if any.

There is a thread with a large number of complaints about the underpayment penalty form, so check the results very carefully. Many people are identifying calculation errors and this form has not been released for filing yet (as of 2/22/21.)

You can file your taxes without the underpayment penalty form and the IRS will calculate it for you. They do not however apportion your income between quarters if you have had uneven income. This might affect you if you have had some lumps of income in different quarters.

I hope this helps. The main thing at this point is to be sure you pay what you owe even if you don't file before 4/15/21, to avoid possible additional penalties and interest.

[agriagro]

To clarify a bit, should I still pay the estimated tax I owe for the last quarter separately to the IRS, even if I've missed the deadline? I was wondering if I could just pay what I owe while doing my taxes through TurboTax instead of making a separate payment.

[Spino]

Just pay what you owe, the sooner the better. It's too late to make estimated tax payments for last year.
You can, however, pay before you file if you need to do that.