My experience with TurboTax was that in two subsequent runs on the same tax year the refund I got would vary by 20-50% (I had to start over at one point). I did

My experience with TurboTax was that in two subsequent runs on the same tax year the refund I got would vary by 20-50% (I had to start over at one point). I didn't dig in: and the reason I was using TurboTax is that I didn't care. So I'll take the IRS heuristic: better than the Intuit heuristic.