system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5, Why do we get tax returns, why can't it just be calculated automatically when paid?

I am British, immigrated to America, and I work. I am delighted every year when I figure out that I get a nice tax return.
I don't have much in terms of deductions, I am married, and that is about it.

In the UK, I never got a tax return, infact, it is mostly automated if your are paid by PAYE.

Can someone explain to me how when I am paid electronically, how either the IRS, or my organization messes up so badly that I end up with thousands in a tax return...

Definitely not complaining, I just don't understand.
gpt
If you're getting thousands in returns with no deductions, you're setting up your withholding wrong. For people with earnings not from a single job (because they work multiple jobs, because they freelance on the side, because they have investments) or who have deductions (because they donate a lot to charity, because they own a home and are paying down a mortgage, because they are paying for education, and so on), there's pretty much no way to track everything ahead of time.

The reason the tax forms default to witholding too much is because they figure people would be more willing to file if they get money back than if they'd owe a bunch of money (which they may have already spent).