Primary care academics back Pulse patient survey
Practices could be out of pocket by as much as £20,000 because of a major error in the way their basic income has been worked out.
Problems with the formula used to calculate practices' global sum payments mean most practices have either been under- or overpaid.
Practices in areas with a fast-growing population have been worst affected by the
error in the 'normalisation' formula, which sets income according to weighted list size.
GPs in these areas have found that although their actual list has grown or remained constant, their weighted list which is adjusted to reflect the workload involved in treating those patients has fallen.
The issue has emerged in the past two weeks because weighting adjustments using normalisation are made on
a national level in April by comparing changes in PCT populations.
For the other three quarters, they are calculated according to changes at a practice level within each PCT.
Many GPs will also have been significantly overpaid and face having to pay back the money at some point.
GPC negotiators have pledged to tackle the issue as part of the review of the GMS contract, but admitted it may be next year before the extent of the problem is known.
Dr Nigel Watson, chief executive of Wessex LMCs, said his practice in New Milton, Hampshire, was £20,000 down. His PCT's population rose by 200, but its weighted population fell by 5,500.
He said: 'To say I am piss-ed off is an understatement. There's no guarantee we'll get anything back. It depends whether the formula has been applied appropriately.'
Dr Eric Rose, a GPC member on the review team looking at the global sum allocation formula, said his practice in Milton Keynes had lost out.
He said: 'I suspect there are lots of other practices this
affects but the problem is that I don't think people look at their quarterly figures.'
GPC chair Dr Hamish Meldrum said: 'The principle of normalisation is quite sound but the implementation has thrown up some problems.'
The latest problem comes on top of glitches in the Exeter payment system which have led to practices with fast-growing lists being underpaid.
By Rob Finch