[refurb]

The issue is that US tax code is based on a lot of information the IRS doesn't have access to - disability, number of child, marriage status, etc.

And then the other issues is that the information the IRS has comes from 3rd parties like your employer, your financial institutions, colleges, etc. That information can have errors in it, so you need to review everything and make sure it's correct anyways.

This happened to me when I worked in a country that automatically filled out your tax return - I pulled together all the information just like I would in the US to make sure it was correct. And guess what? My employer made an error that would have cost me several thousand more in taxes!

So the benefit is really pre-filling a form with numbers. Otherwise the work is very similar to just doing your taxes on your own anyways.