How did they "totally mess up?" TT guarantees its calculations, but is not responsible for user mistakes. Could you have made a data entry error, or forgotten to claim some income? Or maybe the IRS denied your Recovery Rebate Credit.
Maximum Refund Guarantee or Your Money Back
If you get a larger refund or smaller tax due from another tax preparation method, we'll refund the applicable TurboTax federal and/or state purchase price paid. TurboTax Online Free Edition customers are entitled to payment of $30.
