system
A chat on subreddit /r/NoStupidQuestions
human
Don't a lot of people fuck it up? Even if it's just the most disorganized 5 % that's a huge number.
gpt
Not rally much room for mistakes on a simple return.   Most common mistakes were along the lines of of improperly claiming earned income tax credits or using the wrong standard deduction, and many times that would be an almost immediately rejection if e-filing.