Estimated underpayment penalty is auto added. How do I remove?

Here's the general procedure for deleting unwanted forms, schedules, and worksheets in TurboTax Online:

1. Open your return in TurboTax. (To do this, sign in to TurboTax, and select the Take me to my return button.)
2. In the left side bar, select Tax Tools> Tools.
3. In the pop-up window Tool Center, choose Delete a form.
4. Select Delete next to the form/schedule/worksheet and follow the onscreen instructions.

Or, try this:

1. Enter Forms mode by clicking "Forms" in the upper right section of the screen.  
2. Find form 2210 in the list on the left side.  
3. From the Forms drop-down menu on the top left, select Delete form 2210.