The system will underpin Monsoon's preparation for the 1 January chip and Pin deadline, after which retailers will become responsible for the costs of credit card fraud if they are not chip and Pin-enabled.
But the company would not comment on whether it would have chip and Pin systems fully operational by the deadline.
Monsoon IT director Dave Metcalfe said, "Managing a rapidly moving retail business needs systems that can cope with change. Our previous store system had become too inflexible and costly to develop and could not support new initiatives such as chip and Pin."
The system uses the Java 2 Enterprise Edition open platform and standards. The roll-out completes a process begun in 2002, when the company began its search for a new retail system for shops that vary in size and infrastructure from a single point of sale to multiple sales points with a server. Implementation followed a pilot project conducted earlier this year.
Metcalfe said feedback from the company's 4,500 staff has been positive. The system enables Monsoon to run its entire chain of shops using Retail-J's Estate Manger system from its head office in Paddington, west London. Trading information is relayed from the stores to head office throughout the day.
Monsoon is set to extend the system to its stores in airports, enabling the handling and management of flight files, passenger destinations and duty-free sales.
The next phase of the project will deliver 400 handheld terminals to help stores manage their inventory.