Prior to the implementation of the Unique Entity Number (UEN) in 2009, entities such as businesses, companies and societies used a variety of different identifiers. This included the ACRA number issued by the Accounting and Corporate Regulatory Authority (ACRA) to registered companies, businesses and limited liability partnerships, the ROS number issued by Registry of Societies (ROS) to registered societies, the Central Registration (CR) number issued by the Department of Statistics to various categories of entities as required for survey or statistical purposes, and the CPF employer number issued by the Central Provident Fund Board to all employers.

A Single Identity

In order to switch to an one-number only system, the ACRA number that was issued to about 85% of entities was assigned as the UEN for businesses and local companies registered with ACRA. The remaining 15% of entities such as societies, embassies, representative offices, and mutual benefit organisations, which did not have ACRA numbers (as they are not registered with ACRA) have been issued with a new identifier as their UEN.

By January 2009, all entities were issued with their UEN, and all government agencies have adopted UEN with effect from July 2009. To facilitate the transition to UEN, conversion software that maps the UEN to existing identifiers were provided to public, private and social sector agencies.

UEN