What us the underpayment penalty

The underpayment penalty is assessed if you did not pay enough tax throughout the year, either through withholding or by estimated tax payments.

 

• You avoid this penalty if you either owe less than $1,000 in tax or 
• If you paid 90% of your 2019 tax or 100% of your 2018 tax.

For more information, refer to Publication 505, Tax Withholding and Estimated Tax.  or the instructions to Form 2210 for waivers allowed.2019 Instructions for Form 2210

You reply correctly stated that there is no penalty for underpayment if one pays at least 90% of what one owes by Jan 15.  Why, then, does Turbo Tax calculate a penalty when I clearly made the 90% threshold.

  roygo

 

Did you pay your tax through estimated payments?  Were they paid on time?  

 

If you don't pay enough tax through withholding and estimated tax payments, you may be charged a penalty.

 

You also may be charged a penalty if your estimated tax payments are late, even if you are due a refund when you file your tax return.