Which of the following information forms may contain the declaration of someone that your earnings are "income" because they derive from federal privilege?

Each of the information forms (W-2, 1099, K-1) may contain someone's testimony that your earnings derive from federal privilege, and, if so, can be used by the IRS and in court as evidence of such. On a 1040 with non-zero entries for any of the taxable amounts, it is your testimony.

In some cases, the testimony is correct; federal salaries, interest payments from government bonds and federally chartered banks, federal retirement payments such as Social Security, and many other payments from federally-connected activities do indeed derive from federal privilege.

But the larger share of individuals' earnings is not federally-connected and this testimony is in error. However, the courts do not care.