It should be super simple... We have all the math to make it happen, just take the correct amount out of people's checks and leave them the fuck alone.
Don't put your hand in my pocket 26 times in a year then come to me at the end and go "(Blush), sorry, I took too much/too little."
It's a little more complicated because of itemization.
The standard deduction should be pretty simple. For people that give a bunch of money to accountants ... you're probably better off just taking the standard deduction anyways. But eh maybe not.
In theory itemization is a good option, it does save me some money, and there's very little way for the government to know that I e.g. donated to X and that reduces my tax burden by Z. My neighbor tells me back in the day you could itemize a lot more stuff, but those days are gone.
Definitely support the IRS providing some free tax filling software at the very least. There's really no reason electronically filing should cost all the money it does to go through e.g. TurboTax and scare you with the up selling to protect you from audits or XYZ thing.
Not if you take any form of assistance, make any purchases for a business/education, get income from multiple places, work in multiple states, have health insurance, or even received tax credit from a previous year where the government took too much.
All employers report income and deduct taxes from paychecks directly, so the government knows how much you have paid.
What they don't know is if you've won a lottery, sold a service or have someone bunking at your place paying rent. This you need to declare yourself.
In the UK the rule is: we will assume you have nothing else, please let us know if you have additional income
In the US (and Canada) the rule is: we will assume you have a lot of shit, please let us know even if you don't have additional income.
The US system stems from Conservatives having nothing other to run on than "people are going to grift and if you're an honest employed american you have nothing to worry about". Which is a measure that mostly affects the poor and those who don't know the law.
The same reason healthcare was tied to employers. They convince people nothing could go wrong because only those working should have healthcare. Which we can all see is insane but looks good on paper.
Knowing the correct solution and knowing whether or not a solution is correct are not the same thing. Doesn't really apply here, but it's important to remember.
Likewise in the UK for standard wage workers. Only gets more complicated if you have investments outside and ISA or multiple sources of non-labour income.
I never understood why there wasn't a federal web site where you input your gross based on W2. Then check off boxes for special deductions like kids. And wamo here's what you owe. But if our tax system was simple and stupid than thousands of people at IRS wouldn't have jobs. Too bad. Let them find other jobs.
The IRS is (supposedly) under funded. That's (supposedly) why they can't actually go after the rich people and business. They can't afford the legal fees.
The reason there's no federals site is corporate lobbying. You see if there was federal site, business like Turbo Tax and HR Block would fail. They convinced the government "let us take care of the online platform", the gov said "okay, but as long as you make a free service for low income people".
Then the corps branded the free version a different name, burried it and advertised the paid one. Then they filled the service with all kinds of dark patterns to get people to pay for crap they don't need. Government hasn't done anything about it.