The Chicago Tribune reports that U.S. authorities are seeking information from Citigroup Inc.’s Citibank NA and Bank of New York Mellon Corp to uncover the identities of U.S. citizens who may have been hiding money in Swiss bank accounts to avoid taxes. On Wednesday, the U.S. Attorney for the Southern District of New York requested permission to issue "John Doe" summonses to the two U.S. banks for records of the correspondent accounts of Swiss bank Zuercher Kantonalbank (“ZKB”). The IRS uses "John Doe" summonses to get information on possible tax law breakers whose identities are unknown. By issuing the summons, the IRS has demonstrated its move to tighten tax law enforcement and demand more openness and cooperation from Swiss banks. In December 2012, a federal grand jury indicted two ZKB bankers and a former employee over charges of conspiring with American clients to hide more than $420 million from the U.S. IRS.