Comment by dlcarrier

No tax software or expert will never produce a wrong answer, because too many questions have no guaranteed right answer, due to inconsistent interpretatios within the IRS.

Tax filing is a matter of risk balancing, which heuristics are great at optimizing, if they incorporate enough data. Neural networks are ideal for that, but it would take a lot of data gathering to develop the model, from data that isn't easily scraped from Web pages.