The full annual charge agreed upon at the time of contract signature in May 1999 for the Bishop Auckland General hospital private finance initiative (PFI) scheme was £8.1 million per annum. This is uprated annually by the retail price index (RPI) and the cost in 2005-06 was £9.4 million per annum. In addition to changes as a result of RPI, the payment mechanism in a PFI contract contains a volume element under which the quantity of variable items provided by the private sector contractor and charged to the trust, such as meals or linen, is directly related to the throughput of patients.