You do not get a refund from TT if the IRS changes your refund for some reason due to your own user error. The IRS can change your refund if they find a mistake you made. TurboTax guarantees that its calculations are accurate--but the calculations are based on the data that is entered by the user. If you enter something incorrectly or omit income, etc., that is user error. And of course TurboTax never knows about offsets to your refund for back taxes or child support etc. that you owe which might result in a refund offset.