Self-employed persons have to pay taxes on the first $106,800 of combined wages, tips, and net earnings (subject to minimum earnings of a mere $400). This year, the rate is 13.3%. Only half of that amount can be claimed as an exemption on gross income, which means that a self-employed person is effectively penalized for not working for someone else, especially if they have a low income. Other business exemptions for income tax also do not apply.
There is no legitimate justification for maintaining this tax as it is. It effectively helps corporations at the expense of small businesses and individuals.