We could also ask how the government could later tell someone they improperly deducted something! The government can either use that same means to tell taxpayers in advance, or else we could figure out a superior taxation system that wouldn’t require these steps.

You being personally ignorant of this specific argument which gets litigated every single time this comes up but only by Americans because most other countries have zero difficulty doing exactly that is not a valid argument.

91 percent of American filers take the standard deduction. The IRS already has all their information, already knows how much they withheld, already knows what they owe back. For all these people, TurboTax is just filling in 10 fields in the standard form.

"All your tax deductibles" is irrelevant for the vast majority of the country, and always has been.

The 35 million remaining americans who do itemize are free to continue using this old system while the rest of us can have a better world.

By knowing all your tax deductibles?