For purposes of the NIIT, income from passive business activities is defined as "investment income" unless:

a. substantial portion of the business activities occurred in the taxpayer's place of residence.

b. the taxpayer has a specialized license or permit to work in the trade or business that generated the income.

c. the income was derived exclusively from real estate transactions.

d. the income was earned in the ordinary course of a trade or business and is not passive with respect to the individual taxpayer.