Background Given the paucity of relevant data, this study estimates the cost of intellectual disability (ID) to families and the government in Australia.

Method Family costs were collected via the Client Service Receipt Inventory, recording information relating to service use and personal expense as a consequence of ID. Government expenditure on the provision of support and services was estimated using top-down costing.

Results A total of 109 parents participated. The cost of ID in Australia is high, especially for families. Total economic costs of ID are close to $14,720 billion annually. Opportunity cost of lost time provided 85% of family expense. A comparison of family expense and social welfare benefits received suggests that families suffer considerable loss. This may impact on families’ physical and emotional wellbeing.

Conclusions Monitoring of changes in expenditure is required. Policies should ensure that money devoted to ID is allocated in a rational, equitable, and cost-effective manner.