QuickBooks Dictionary
Income effectively connected
All income from U.S. sources which is effectively connected with the conduct of a trade or business in the United States is taxed to nonresident aliens and foreign corporations at the same rates as apply to U.S. citizens and domestic corporations. Investment and other fixed or determinable periodical income (interest dividends, rents, wages, etc.) of a nonresident alien is taxed at a flat 30 percent rate, whether or not the recipent engages in a trade or business in the United States, so long as such income is not effectively connected if it is derived from assets used in, or held for use in, the United States, and if the activities of the U.S. business are a material factor in the realization of the income.