Skipton, which has 80 branches nationwide, will base all its future IT on a development platform and database from Jade Software.
The software is designed to convert the Building Society's Unisys systems running Linc, a 24-year-old programming language. Skipton plans to use Jade in a number of developments.
Skipton's first major project is a multimillion-pound transition from its Linc mainframe system to Jade in a bid to save on ongoing operating costs and providing a web-enabled IT platform. Jade Software said it is also developing a new branch automation system for the society's branches.
Over the past three years Jade has provided Skipton with customised mortgage, investment and customer relationship management applications.
Jade founder Gil Simpson developed Linc, a Unisys mainframe language, with his colleague, Peter Hoskins in 1978. Unisys, which bought Linc from the developers in 1980, still supports about 3,500 Linc systems worldwide.