The Portrait Series of currency notes is the fourth and current set of notes to be issued for circulation in Singapore. It was first introduced on 9 September 1999 by the Board of Commissioners of Currency Singapore (BCCS), whose role was since taken over by the Monetary Authority of Singapore (MAS) post-merger. This series features the portrait of Yusof bin Ishak, the first president of Singapore. The design has been simplified and new security features were introduced. Polymer versions of this series were released for general circulation by MAS as of 4 May 2004.