The global economy is becoming increasingly integrated, and companies are routinely able to access markets throughout the world. For decades, the United States has maintained a robust economy and a strong market for imported goods. This article discusses some of the basic U.S. federal income tax principles that apply to non-U.S. companies doing business in the U.S. Later articles will explore common strategies for entering the U.S. market, monetizing and protecting intellectual property, and other topics relevant to companies entering the U.S. market.