Citigroup is getting out of the master trust business in the U.S. The firm sent a letter to its U.S. pension fund clients informing them that its services would end and the end of the year. The company will continue offering its trust and pension servicing businesses to clients outside the U.S. Nina Das, a Citigroup spokeswoman, said only about 80 clients would be affected. The firm provides master trust services for U.S. pension fund clients with a total of less than $65 billion in assets under custody. Citi has a total of $13 trillion in global assets under custody. Once Citi acquired BISYS Group, which provides fund servicing, Citi decided to leave the master trust services business, Ms. Das said.