How does TurboTax calculate the underpayment penalty if form 2210 isn’t used?

[JohnnyJohnny13]

I there a way to see how TurboTax is estimating the underpayment penalty if I’m not annualizing (i.e. no form 2210). I downloaded all the forms and worksheets but I don’t see anywhere how that number is calculated. 

[JohnnyJohnny13]

Actually I think form 2210 exists. I just can't see it as it won't download with the forms (I suppose to prevent me from filing as it's not required). I know this because it shows up in the forms I can delete. Unfortunately I can't download individual forms using the online version *sigh*

[JamesG1]

In TurboTax Online, to view IRS Form 2210 in your 2021 Federal 1040 tax return, view the forms at Tax Tools / Print Center / Print, save or preview this year's return.

Use IRS Form 2210 to see if you owe a penalty for underpaying your estimated tax. The IRS will generally figure your penalty for you and you should not file Form 2210. You can, however, use Form 2210 to figure your penalty if you wish and include the penalty on your return.