United Utilities' Grasmere House on Lingley Mere Business Park in Warrington is now fully occupied.
The 46,682 sq ft office development is a joint venture between Muse Developments and United Utilities Property Solutions.
The shared service centre is now occupied by the UK's largest listed water company, which has relocated a number of its operational and support functions to the purpose built structure.
Property and construction consultancy Acies advised on the project management of the building, which was completed in March 2009.
Paul Foode, Lingley Mere estate manager, said: "We have completed the migration of some 590 staff from various locations across the region into a modern, high spec, energy efficient, purpose built office."
United Utilities' former headquarters, Dawson House, was also located in Warrington on a 12-acre site and was being demolished to make way for redevelopment.
Lingley Mere Business Park offers 1.25m sq ft of business space and related amenity facilities. It currently provides 380,000 sq ft of office accommodation