Objective Current plans in the English National Health Service are to replace block contracts for mental health providers with a single tariff for each ‘cluster’ of conditions. A single tariff will not take into account the potential additional complexity and costs inherent in caring for older people. To examine the basis for a uniform tariff, differences in service utilisation and costs between working age adults and older adults in two populous clusters (non‐psychotic, psychotic) were investigated across five mental health healthcare providers in and around London. Methods Retrospective review of records over 3 months assessing service utilisation and costs using the Client Services Receipt Inventory. Results Records of 362 patients were reviewed, 179 older adults (90 non‐psychotic, 89 psychotic) and 183 adults of working age (83 non‐psychotic, 100 psychotic). Older adults in both clusters had more tests, assessments and home visits. Overall costs of care of older adults were significantly higher in the non‐psychotic cluster (£5634, vs £4405 psychotic, p = 0.044). Conclusions An appropriate age‐related tariff is required for each cluster. Copyright © 2016 John Wiley & Sons, Ltd.