Barclays has signed a six-year IT outsourcing deal with Accenture valued at more than £400m.
The contract to outsource the bank's application development division is one of the largest UK outsourcing deals this year and follows at least nine months of negotiations.
Plans by Barclays to outsource its application development division, Build Services, were first revealed by Computer Weekly last August.
Nine hundred IT staff will transfer to Accenture over the next year and there will be no compulsory redundancies in the first two years of the contract.
Barclays will retain overall responsibility for IT strategy development and will maintain staffing in selected areas.
The bank said the project will help it respond quickly to market demands for changes in technology and lower the cost of developing and maintaining its software applications.
The deal with Accenture is part of a long-term strategy by Barclays to outsource the bulk of its IT to different suppliers.
Last year, Barclays outsourced the management of its desktops to EDS in a $350m (£214m) IT outsourcing deal.
Commenting on the Accenture deal David Weymouth, chief information officer at Barclays, said. "Working with a recognised leader in global technology capability is an important step in ensuring that we deliver top-quartile capability and productivity in the vital area of systems development."
Keith Brookes, national secretary for banking union Unifi, which represents IT staff at Barclays, said the union was happy with the deal although negotiations had been tough.