You can enter $20,757 in the Cost Excluding Tax box, and $376.85 in the Sales Tax Paid box. Leave the Sales Tax Percent blank.
The $376.85 in sales tax actually paid is the result that should display in the “Deduction Allowed” section of the following screen. It appears there may be other fees that were taxed in your purchase to total this sales tax paid amount. And because you have a trade-in that exceeds the amount of your purchase, entering the net result in TurboTax may not calculate the same sales tax you actually paid.
Here is additional clarification to what each box on the Enter Major Purchases screen is asking.
Cost Excluding Tax: What is the total paid for your purchase, including dealer fees, warranties, and other charges, after your trade-in allowance, and before sales tax is added to this amount.
Sales Tax Paid: The sales tax amount paid, which is shown on the sales receipt for your car purchase.
Sales Tax Percent: What is the sales tax percentage shown on your receipt? If this is available, enter the percentage. If it is not available, then leave it blank. TurboTax will calculate the percentage using the amount in the prior two boxes.