The delivery will initially implement the Phoebus solution within the Kent Reliance business and is due for completion by the end of 2014.
Products that will be supported through the delivery include residential mortgages, buy-to-let, equity release, commercial mortgages and Channel Island mortgages.
The implementation will be undertaken at OSB’s Head Office in Chatham and for various servicing activities in OSB’s India operation.
Paul Hunt, PSL’s managing director, said: “This client win is testimony to the strength and depth of the Phoebus solution.
“For example, one of the proven strengths of the Phoebus solution is its ability to originate and service many different lending and deposit products off a single platform and database.
“Following the initial KRBS delivery, this will allow other OSB Group companies to have the capability of running off the same solution in the future. We look forward to working with OSB over the next five years and beyond."
Richard Davis, KRBS’s IT director, added: “The high degree of automation the Phoebus solution will achieve within OSB will assist us in optimising operational efficiencies in many areas.
“We believe PSL offers a combination of a tried and tested platform supported by a high level of migration expertise and the flexibility to develop our systems as our product offerings expand.”