Nationwide, the world's largest building society, is preparing to transfer customer data in several major system migrations in the next month.
As part of the company's £1 billion Voyager technology transformation, Nationwide has created a new mortgage platform and internet banking site.
Today, Nationwide said it was nearing the end of moving customers onto its new internet platform, with the migration due to be complete in two weeks.
By the new year, the building society expects to extend its new mortgage platform to all branches - including the Dunfermline, Derbyshire and Cheshire building societies, which it completed integrating last month. Until now, the mortgage platform had only been used by intermediaries. It will also replace its current account system.
As Nationwide reported a 17 percent rise in pre-tax profits ot £172 million, for the six months to the end of September, it said the system changes were improving "product innovation and customer service".
The new internet bank was "more intuitive and provides customers with enhanced service and functionality," it said.
"We are well advanced with our preparations for the implementation of the Payment Services Directive 2012, and we will replace our personal current account system next year, which will allow new product offerings and enhanced services to our current account holders."
Last month, the building society announced it had fully integrated the Cheshire, Derbyshire and Dunfermline building societies, which it acquired in 2009 as the financial crisis deepened.
Nationwide has also slashed ISA application times, launched new credit and debit cards, and constructed what it calls a "state of the art" data centre.
The Voyager programme is being run by IBM and IPL, with SAP software acting as the basis for many of Nationwide's platforms