From 5 January 2015, all practices will be able to register patients who live outside their boundaries, without being required to provide home visits or out-of-hours care.
If these patients require GP services in the area where they live, local practices will be offered £16 per in-hours consultation and £60 per home visit under an enhanced service.
Practices will not be obliged to participate - they can refuse to register out-of-area patients and will not have to offer home visits or consultations for those registered elsewhere.
200,000 patients could take part
NHS England expects about 0.4% of the population - 200,000 people - to register with a practice outside their local area, admitting 'this might grow over time'.
Any patient who requires 'urgent and local care' and cannot travel to their out-of-area practice will be able to access primary medical services nearer their home, under the new enhanced service.
The GPC warned it had 'lots of concerns' about the plans and said practices would have to decide whether the remuneration was 'enough to cover their costs'. GPC deputy chairman Dr Richard Vautrey told GP the scheme could lead to patients choosing to register in areas where the local CCG provides treatments not available in their area of residence.
'If you happen to work in a CCG area that funds IVF, whereas the neighbouring area doesn't, it's possible patients will choose to register with practices in the area that do. That will have a knock-on effect on your own practice budget and CCG budget,' he said.
Conversely, patients could find themselves unable to obtain a treatment in their registered practice area which is available under their home CCG.
Practices accepting out-of-area patients will initially receive funding in line with that for other patients.
But NHS England has said it could cut this, to offset the cost of providing urgent care services. Any changes, it said, would be subject to discussion with the GPC.
Dr Vautrey said the GPC would oppose any attempt to reduce funding for out-of-area patients after practices have registered them.
He warned that if area teams are unable to persuade enough practices to sign up to the enhanced service and other providers are required, it would exacerbate the fragmentation of the urgent care system.