Definition:
A U.S. Branch of a Foreign Bank or Insurance Company is a branch located in the United States of a bank or insurance company that was organized outside of the United States. A US branch of a foreign bank must abide by special rules subject to Federal Reserve Board supervision. A US branch of a foreign insurance company is subject to state regulatory supervision. If a US branch of a foreign bank or insurance company agrees to be treated as a US person, it must provide a Form W-8IMY. NRA withholding and FATCA withholding will not apply to payments that can be reliably associated with a Form W-8IMY from a US branch of a foreign bank or insurance company in this case.
A payment to a U.S. branch of a foreign bank or a foreign insurance company is presumed to be effectively connected with the conduct of a trade or business in the United States if the withholding agent has an EIN, generally provided on a Form W-8ECI by the branch. This presumption does not apply if the branch provides a withholding agent with a Form W-8BEN-E for the income. Although the branch will be treated as a US person, payments must be reported on Form 1042-S.