The Chancellor of the Exchequer asked the National Audit Office to audit two new assumptions underlying the Treasury's fiscal projections within the 2009 Budget (HC 407, session 2008-09, ISBN 9780102959161). Firstly, to assess if the 2008 Pre-Budget report assumption for the trend rate of growth, allowing for a downward adjustment to the trend output level of around 4 per cent, for the post-2006 period, together with the further downward adjustment at Budget 2009 to the trend output level of around 1 per cent, is reasonable and cautious. Secondly, to examine whether the approach used by the Treasury to produce estimates of the fiscal aggregates adjusted for the effects of the economic cycle is reasonable.