For 2020, I paid 100% of the taxes I paid for '19 tax year. My understanding is that I shouldn't have to pay any estimated tax penalty. TT is applying a penalty. ??

Generally, an underpayment penalty can be avoided if you use the safe harbor rule for payments described below. The IRS will not charge an underpayment penalty if you pay at least:

• 90% of the tax you owe for the current year, or
• 100% of the tax you owed for the previous tax year.

This rule is altered slightly for high-income taxpayers. If the adjusted gross income on your previous year’s return is over $150,000 (over $75,000 if you are married filing separately), you must pay the lower of 90% of the tax shown on the current year’s return or 110% of the tax shown on the return for the previous year.

However, if you do not pay at least that much via quarterly estimated payments, you may be subject to an underpayment penalty.

You might be able to eliminate it or at least reduce it. You can go to Federal Taxes tab or Personal tab, under Other Tax Situations and select Start by the Underpayment Penalties. You will answer a series of questions that may reduce or eliminate the penalty. Or you can elect to have the IRS figure the penalty for you. It's form 2210.

It's under

Federal or Personal (for Home & Business Desktop)

Other Tax Situations

Additional Tax Payments

You need to enter estimates you paid?  You probably won't have a penalty once you enter the estimates.  

You can type estimates paid in the search box at the top of your return and click Find and it will give you a link to Jump To it.

OR

To enter Federal or State Estimated Taxes Paid, including a state estimated payment made in January for the prior year, go to

Federal on left or at top. Personal (Home & Business)

Deductions and Credits at top

Then scroll way down to Estimates and Other Taxes Paid

Estimated Taxes - click the Start or Update button

Underpayment Penalties - Click the Start or update button

Thanks. I found where to enter the estimate tax payments. I paid 100% of 2019 taxes for 2020. Yet, it's still estimating a tax penalty. Stumped.