Agree with all of them except the kids. That was the big reason I said "huge percentage" instead of something like "overwhelming majority", because I have a sneaking suspicion the IRS doesn't know anything about your kids at all. So I'm guessing child tax credit isn't automatically calculable right now.
Let's assume you're right that they don't have a simple table that shows parentage of every SSN, sounds plausible that they wouldn't at least to start, but on the other hand, (for people who don't add or remove spouses or kids from their household) it's arguably VERY common for kids to persist with the same parent(s) from one year to the next.
I don't think anyone is saying "All taxes should be automatically calculated to the final numbers" -- just that for instance, when I filed last year with a spouse and 2 kids, a default calculation could be done this year that assumes an unchanged household.
And anyway, just as TurboTax does, the IRS could maintain a simple fact database for you for you to sign in and indicate what SSNs are part of your household, with the bonus that it would detect a duplicate claim for the same kid up front and show you that someone else (e.g. your ex) is claiming them and that you should get them to remove them to avoid both your returns being incorrect. The complexity for a taxpayer of signing in to IRS to manage household members, address, etc. with IRS is an order of magnitude less than that of tax prep they have to do today.
The IRS does it anyways to validate your return ...
It's marginally more work for them to tell you the results of their math. And compared to how many people file taxes it's a net benefit for society. Collectively paying a small group of people to do something for the benefit of many is like the whole point of government.
They can make a likely guess (the full year), and you tell them if they're wrong.
> whether you took college courses?
Yes, your college files Form 1098-T to tell the IRS this.
> how much you put into your IRA?
Yes, your IRA custodian (your bank) files Form 5498 to tell the IRS this.
> which purchases count as medical expenses?
Very few people spend enough on medical expenses to take a deduction for them. They have to exceed 7.5% of your AGI.
> the cost basis of the stock you sold?
Yes, your brokerage files Form 1099-B to tell the IRS this. There are only a few rare cases where they won't be able to report a cost basis.