The General Medical Services (GMS) funding formula (Carr – Hill formula) is an attempt to fund practice workload, regardless of the population they serve. It is applicable to the vast majority of the UK, but there are some practice populations that are so significantly atypical that using the GMS funding formula would not ensure the delivery of an adequate general practice service. This working group has looked at three such atypical populations: unavoidably small and isolated; university practices and; those with a high ratio of patients who do not speak English.