The United States Treasury is a department of the government of the United States of America. The Treasury prints and mints all the U.S. currency in circulation around the world. They also investigate cases of tax evasion, money laundering, and other related crimes.
Before Season 3[]
The U.S. Treasury found out about the extortion to a businessman in San José at the hands of the Armenian Mafia. They then convinced him to let them introduce $50,000 marked, traceable bills in his payment to the Armenians. They planned to trace the money and see what banks were handling their transactions. However, in three months not a single bill had surfaced.
Season 3[]
The Armenian Money Train heist carried by the Strike Team ignited a series of murders by the Armenian Mafia who were retaliating while looking for those responsible for the heist. When Detective Dutch Wagenbach and Claudette Wyms started investigating the murders, the U.S. Treasury sent Agent Quigley to the Barn to help them with their investigation, because of their knowledge on the Armenian Money Train.
When some of the marked bills surfaced in the middle of a case of contraband against the Byz Lats, Treasury sent Agent Crosby Nell to the Barn to question the main suspect.