The 1099, W-2, K-1, and similar information forms get their power to become evidence that the earnings declared are income and federally-connected from:

The tax forms listed are filed under great pressure from the IRS. They are all that is needed to legally enforce the collection of taxes on your earnings as if they were derived from federal privilege, whether they are or not.

You are never told that the terms on the forms such as "wages", "employee ", and "trade or business" are terms of art , defined very cleverly in the tax code to conform to the law, yet give you the impression that your private-sector earnings are taxable. You cannot read the tax code and understand it without careful study of the definitions in the code of these terms (Fortunately, someone has done this for you; more information later).

Also, you are probably unaware that the courts, unless given evidence otherwise, presume that any earnings you receive are federally-connected. This dooms any case you might make that you do not owe the tax unless you rebut this presumption.

But you shouldn't be upset; after all, you are supposed to know the law, are you not?