How do I know the blended tax rate is accurate?

[chad-whisman]

Where does the blended tax rate come from?

[GeorgeDenseff]

You can compute it yourself with a calculator.

Your blended tax rate is the amount of tax you paid (or will pay) for the year, divided by your adjusted gross income (AGI). 

[SundayInSalem]

TurboTax backs its tax calculations with a 100% Accurate Calculation Guarantee. In plain English, if you pay an IRS or state penalty or interest because of a TurboTax calculation error, TurboTax pay you the penalty and interest.

See: What is the TurboTax 100% Accurate Calculation Guarantee?