The business rates retention scheme (BRRS) was set up in 2013-14 to provide English councils with stronger incentives for growth. Initially, councils bore (up to) 50% of the real-terms changes in local business rates revenues.
Of course, as well as providing stronger incentives, such a system poses greater risk of divergences in funding, as different areas may see revenues perform differently.
Just over two years later, George Osborne announced that in order to further strengthen incentives, councils would bear 100% of the real-terms changes in local business rates revenues from 2020. In April 2017, four city regions (and Cornwall) began piloting what the Government calls 100% retention in anticipation of the planned national roll-out.