Cleveland Police Authority has become the first customer of Steria's shared services offering that is targeted at UK police forces.
The authority is spending £175m over the next decade on shared services and expects £50m in savings in that time.
The deal is the first of its kind for Steria, which is targeting a shared services model at police authorities across the UK.
Cleveland will be the first police body to use Steria to share services such as finance, HR, payroll, commissioning and fleet management in Steria's dedicated datacentres. When other forces are signed up they will use the same infrastructure.
The £50m cost savings come from efficiencies but there was no redundancies.
A total of 470 civilian staff at Cleveland Police Authority moved to Steria with more than 200 remaining at the police authority.
Steria was up against Capgemini and Reliance in bidding for the contract.
Sean Price, chief constable at Cleveland Police, said the deal aims will save time and money, and "will positively impact the services we can provide to local residents".
Steria already works with half of UK police authorities through its Storm command and control system.
John Torrie, CEO at Steria UK, said the deal is the first of its kind for Steria and is part of a wider public sector push. "We have been in the police sector for over 30 years but police authorities have not outsourced as much as they could."