Michigan Compiled Laws, Chapter 208. Business Tax § 208.1115

(a) The transfer of title to, or possession of, property that is stock in trade or other property of a kind that would properly be included in the inventory of the taxpayer if on hand at the close of the tax period or property held by the taxpayer primarily for sale to customers in the ordinary course of the taxpayer's trade or business. For intangible property, the amounts received shall be limited to any gain received from the disposition of that property.

(b) The performance of services that constitute business activities.

(c) The rental, lease, licensing, or use of tangible or intangible property, including interest, that constitutes business activity.

(d) Any combination of business activities described in subdivisions (a), (b), and (c).

(e) For taxpayers not engaged in any other business activities, sales include interest, dividends, and other income from investment assets and activities and from trading assets and activities.