California almost had such a system. NPR's Planet money did a great episode on this called Tax Hero: https://www.npr.org/sections/money/2019/04/03/709656642/epis...

Description below is from the podcast episode page:

> Back in 2005, a group in California decided we could make filing taxes dramatically simpler in the US as well. Lots of Americans could receive tax forms in the mail that were pre-filled out by the government. All they'd need to do is check for errors and send the forms back in.

> Joseph Bankman, a law professor at Stanford, thought this was such a no-brainer, that he offered to test out the idea with some California taxpayers. It turned out to be a huge success. Other states thought about using the plan. Even California's governor at the time, Arnold Schwarzenegger, supported it.

> Bankman thought getting ReadyReturn through the California legislature would be smooth sailing. He was wrong.