Why is this a question? Do you maybe have income reported to on a 1099-MISC with the income reported in box 3 or 7? If so, then as far as the IRS is concerned, you earned that income while self employed and in business for yourself. If this is not your case, and the income is reported in box 3 or 7 of a 1099-MISC, then why were you paid the income?
