Reply To: NIIT SE TAX OR NEITHER ? Home › Fairmark Forum › Equity Compensation › NIIT SE TAX OR NEITHER ? › Reply To: NIIT SE TAX OR NEITHER ? March 26, 2021 at 6:32 pm #17403 caesarkParticipant Kaye, The 2.9% Medicare tax would apply to the entire amount of income, correct. While it is less than the 3.8% NIIT, in this tax return it will be not be a small fraction.