How do I edit/add a major purchase for sales tax deduction? I already skipped over it and now I can't find it to add my new car purchase.

‌In the sales tax section, choose  Easy Guide  and tell the software about the car purchase on the page Enter Major Purchases.

 

Here's how you can navigate to the sales tax entry in TurboTax Online:

 

1. Navigate to Federal > Deductions & Credits > Estimates and Other Taxes Paid > Sales Tax > Start or Revisit

 

If you're itemizing, you must choose between deducting your state and local income taxes or your state and local sales taxes. You can't claim both.