TurboTax is miscalculating my underpayment payment - how can I override?

An underpayment penalty would be entered on line 24 of the Federal 1040.  Are you saying that the entry is zero?  If so, then no underpayment penalty has been calculated.

You can review the 1040 in TurboTax Online by following these directions. 

• Down the left side of the screen, click on Tax Tools.
• Click on Tools.
• Under Other helpful links, click on View Tax Summary.
• Down the left side of the screen, click on Preview My 1040 to see the actual tax return that you prepared.
• Down the left side of the screen, click Back to return.

TurboTax is saying I have a penalty (value is positive in 1040).

When I manually use the Form 2210 to calculate the value myself, following the form instructions I get it to zero, meaning I don't have a penalty. Reason I get zero is when I get to the part of adding my paid tax with my estimated payments before Jan 15. That value is over 90% of my due taxes. Therefore, no penalty.

I think TurboTax is doing something wrong and not considering that. I'd like either for TurboTax to fix this or for a way for me to override as I believe I'm right (well, I'm just following Form 2210 instructions).

You can complete form 2210 in TurboTax to see if you have a penalty for not paying in estimated taxes on time. They are due quarterly. Go to "Other Tax Situations" and find "Underpaid Penalties" under  "Additional Tax Payments."