Itemized deductions are 1040 Schedule A, and you don't typically file worksheets along with your return (although there's nothing stopping you from doing so).

Itemized deductions are far from the only thing that the IRS doesn’t know about. Almost everything on Schedule C, and RSU and ESPP cost basis would also probably require manual intervention. Probably a bunch of other credits as well, like the tax credit for buying an EV, solar/energy efficiency, adoption, various student-related deductions/credits, etc.

Easy to task the seller with reporting when offering the various energy efficiency subsidies.

And I think that's part of the problem. I've done my taxes (in the U.S.) manually for the past couple of years (i.e. filling out a 1040 directly, no TurboTax etc.), and the amount of times I've read through some absurd item that is clearly only in the tax code to get the vote of some special interest is depressing. Like most 'benefits', there would be uproar if you tried to take them away now by the people impacted, but maybe they could be moved out into separate programs.

Seems like getting to a point where ~75% of the population didn't need to file would be doable if there was enough motivation for it. If your only income is on a W-2, and your only mortgage / banking / trading is with U.S. companies like Chase or Morgan Stanley, no reason that couldn't all be done for you.

You took me literally. Basically IRS can file taxes for all your details without adjustments. If you want to make adjustments, there should be an easy way to fill them in and be done with them. Donations, tax credits, etc.

Most brokers send all the info to the IRS, but there are some that get wrong cost basis for ESPP (Fidelity looking at you) and so you’ll have to rectify that too. But those things should spit out a number that gets adjusted from the IRS number.

They'll actually do that today if you want!

I had a friend in college who hated doing taxes so he spent 5 min putting whatever numbers into the forms.

A few months later the IRS sent a "your filed incorrectly, here is the corrected return" and he'd be like "cool".

Even taking the standard deduction, I don't think I've had a year in my life where I didn't have additional tax credits and deductions. You don't need to itemize for some very common situations on top of the standard deduction.