The Workplace Number (which had replaced the previous Factory Number since 19 February 2010), is used for identifying companies and factories in transactions (such as factory or statutory equipment registration) with the Ministry of Manpower.

The Workplace Number will be assigned to you when you apply for a Factory Notification. It takes on this format: Unique Entity Number (UEN) + 4 digits (e.g. 123456789A0001). 

This information is sourced from MOM.