It sounds like the 99% satisfaction rate was "of the people who filed their taxes using ReadyReturn" so it presumably excludes those who observed, or suspected,

It sounds like the 99% satisfaction rate was "of the people who filed their taxes using ReadyReturn" so it presumably excludes those who observed, or suspected, that the result was not correct and made alternative arrangements. That said, I will also admit that this article is really about California state taxes, which are substantially simpler for most people than federal taxes. I got off on a bit of a tangent because Prof. Bankman seems to claim that the same approach will work for federal taxes as well, and in general most people perceive these issues as linked: automatically prepared state taxes are seen as a step towards automatically prepared federal taxes.