The National Health Service (NHS) in England is introducing a national cost-per-case tariff system for the reimbursement of hospital services. Unlike most other countries with similar payment mechanisms, hospitals in England will have few alternative sources of income once the tariff system is fully implemented. This new financial regime generates powerful incentives for change, but exposes purchasers and providers to considerable financial risks. This paper examines the structure of the tariff. We describe how costs are determined, analyse the extent to which prices reflect costs, and review the results of an early evaluation of the system.