I'm annoyed that there is no simple system for the IRS to tell me what I owe, and let me pay or dispute. Instead, we play this game where the IRS provides a bunch of complicated documents, I guess which ones to fill out and submit, then wait 3 years to see if I was randomly chosen to see if I was correct. So it's very easy to make a mistake for dozens of years, then suddenly be penalized at random. It's the worst kin…
Not..entirely true.
My 2016 taxes were professionally done, but we somehow forgot to include one of the something-something-1099 forms from a brokerage firm. The brokerage reported some RSU stock-sells to the IRS but didn't report the cost-basis, and so the IRS assumed the cost-basis was $0 and thus taxed the full sale as income (effectively double-taxing all the RSUs). They just sent a tax bill for something like $20k plus a bunch of fees and interest.
It's an accounting-error so we won't owe much, but I doubt we would have seen this mistake if the IRS had just told us a total amount to pay. We have two tech-job incomes both of which are highly-dependent on equity, so we'd almost certainly end up getting a CPA to run all the numbers again anyway.
I'm a fan of reducing bureaucracy of double-reporting tax info, but I'm personally unwilling to trust that the IRS and various banks / brokerage systems are up to the task of generating trustworthy data (and/or erring on the side of the taxpayer in situations like this).