GPs taking part can boost their income by keeping 10% of any savings they make.
The pilot commissioning clusters will be running cash budgets from July. Seven clusters of GPs have said they are interested in signing up.
In a prospectus to all GPs, NHS Cambridgeshire sets out the risks and rewards.
The Cambridgeshire groups will be expected to return 30-50% of any surplus to the PCT and reinvest 50-70% in patient care.
The money returned to the PCT will be used to 'offset overspends elsewhere'.
Groups that wish to take profit from the scheme for themselves would be expected to balance this by considering placing a deposit or bond with the PCT to cover overspends.
‘These funds would be 'at risk' in that the PCT could draw them down in the event of a cluster over-spending,' the prospectus says.
Dr Guy Watkins, chief executive of Cambridgeshire LMC, said the LMC has worked with the PCT on its plans.
Dr Paul Zollinger-Read, chief executive of NHS Cambridgeshire, presents the prospectus in the context of ‘a very challenging financial period'.
Practice budgets will be set using the PBC national toolkit, the local prescribing formula and the Carr-Hill formula for GMS practices. Practices will then agree with the PCT what proportion of the budget they wish to take responsibility for.
Core GMS and PMS income will at first be excluded to obviate conflicts of interest and cushion practices against losing their core income. Contracts will probably last three years and be reviewed annually.
Clusters can decide whether to appoint a lead practice or form a company, joint venture, limited liability partnership or provident society.
The PCT is ‘keen to explore' clusters in partnership or joint ventures with external partners.