Eh, you can take the standard deduction and the foreign tax credit or any of a bunch of other things that don't always have great information on forms.

A whole lot of preparing a tax return is plugging in numbers from forms that are sent to you and the IRS. It would be simpler (but perhaps less timely) if the IRS sent the taxpayer the return and if you disagreed, you could send in an ammended form with any documentation, or just pay the bill/cash the check.