A pretty damn large portion of people claim the standard deduction. They are paid on W2. Their investments are on 1099s. The cost basis are in supplemental docu

A pretty damn large portion of people claim the standard deduction. They are paid on W2. Their investments are on 1099s. The cost basis are in supplemental documents that could easily be provided to the IRS in a format they can handle. Yeah, it doesn't work for everyone. So they could offer it to you, and you have the choice to click "ok", or to click "add additional income and deduction". If your situation is so crazy that neither of those options work, you can then do it the classic/hard mode way with an accountant. It's how it works in plenty of countries. The US is a bit unique with one of the more complex tax code in the world, but it would still work fine for a large portion of the population.