Mark Erwin is the branch chief in Branch 5 of the I.R.S. Office of Associate Chief Counsel (International), where he specializes in the taxation of foreign financial institutions and cross-border financial products. Prior to joining Chief Counsel in 2006, Mr. Erwin spent several years practicing tax law at firms in Washington D.C. Mr. Erwin has degrees from New York University (J.D.), Princeton University (Ph.D.) and Trinity University (B.A.).