The Net Investment Income Tax is imposed by section 1411 of the Internal Revenue Code. The NIIT applies a rate of 3.8% to certain net investment income of individuals, trusts and estates that have income above certain thresholds.
As a general rule, investment income includes, but is not limited to: interest, dividends, capital gains, rental and royalty income, income from businesses involved in trading of financial instruments or commodities and businesses that are passive activities to the taxpayer.
Your share of income reported on your Form K-1 or 1099-INT and any gain resulting from the disposition of the property may be subject to NIIT. You should consult your tax advisor to determine the impact of NIIT on your personal tax situation.