You have to file a W-4. But you can specify a very high number of exemptions so that your withholding is almost nothing (so I lied, it’s not nothing). But if you do this, you should be scrupulous about paying quarterly taxes so as not to get hit with penalties and interest.
Personally I underpay my bi-weekly withholding by some double-digit percentage. Every year I get a letter warning me to change my ways lest there be consequences. I just add it to the “consequences” pile and pay the entire amount that I owe for the year.
I think that in this case it’s less a question of authority and more one of resources. The IRS is underfunded and understaffed. If they had more resources, would they choose to use them on making tax filing very easy for the fraction of the US that has very simple taxes, or would they do more audits and go after more tax cheats?
So, extending this to answer the OP, possibly the laws that keep this from happening are the appropriations for IRS funding. They could do this, but it’s not trivial and they don’t have the resources, and if they had more resources it’s not clear that this would be the best way to use them.
Right, I mentioned this in post 25 and some others seem to be converging on it. The IRS mostly doesn’t need granular Congressional approval to make changes that aren’t legally binding to taxpayers (the OP proposition would not change the taxpayer’s obligations).
But this would be an expensive proposition that Congress likely wouldn’t sign off on. Republicans want to gut the IRS and make the experience as painful as possible so people will agree to gut it further. Democrats have little appetite for measures that would consume funds without raising revenue. The tax prep industry lobbies Congress to help keep them in business.
Nobody wants this change except a segment of middle-class taxpayers, and they don’t have enough clout to make it happen. So Congress isn’t going to budget it.
If Congress allocates funds to the IRS, the IRS is bound by law to use them in the specified manner.
And the definition of “best use” is a political choice. IIRC in the 80’s, Reagan directed the IRS to make a shift toward economizing the cost of audits… in other words, prioritize audits that were likeliest to produce revenue (as opposed to random audits to reinforce compliance). It seems reasonable at first blush, but the effect was to incentivize people and businesses to structure their businesses and incomes in ways that were too expensive to audit. So, as usual, the middle class is distracted by the shiny bauble of “efficient fiscal conservatism” while the upper class walks off with the loot.
In Japan taxes for employed workers are much simpler and generally companies calculate the taxes for their employees. There are only a few deductions allowed.