The allocation of permits is an important design aspect of an emissions trading scheme. Traditionally, governments have favoured the free allocation of greenhouse gas permits based on individual historical emissions ('grandfathering') or industry benchmark data. Particularly in the European Union (EU), the free allocation of permits has proven complex and inefficient and the distributional implications are politically difficult to justify; auctioning emissions permits has therefore become more popular. The EU is now moving to auction more than 50 per cent of all permits in 2013, and in the US the Regional Greenhouse Gas Initiative (RGGI) has begun auctioning more than 90 per cent of total allowances. Another case in point is the Australian proposal for a Carbon Pollution Reduction Scheme (CPRS), which provides for auctioning a significant share of total permits. This paper discusses the proposed Australian CPRS's auction design. A major difference to other emissions trading schemes is that the CPRS plans to auction multiple vintages of emissions permits simultaneously. Copyright 2010 The Authors. Journal compilation 2010 Australian Agricultural and Resource Economics Society Inc. and Blackwell Publishing Asia Pty Ltd.