The provisioning practices of big banks that get to follow the advanced version of Basel 2 rules versus the practices of smaller banks that must follow a standardised version of Basel 2 got a workout at the investor briefing conducted by Suncorp yesterday.Chris Skilton, chief financial officer of Suncorp, said Suncorp reduced its collective provision to $80 million at June 2008 from $82 million at December 2007 and $95 million at June 2007.Skilton emphasises that accounting standards require history and loss experience to inform the level of the collective provision. He said Suncorp uses a data set that stretches back over 10 years.He speculated that those big banks topping up their collective provision - somewhat along the lines of the general provisioning approach of the former accounting standards - may be able to do so because of quirks of the Basel 2 rules that the Australian Prudential Regulation Authority applies to the big banks.ANZ and Commonwealth have in recent weeks said they topped up their collective provision on the basis of their assessment of economic conditions.Skilton said he'd prefer to go back to the old method of dynamic provisioning, but since Suncorp could not, investors would have to get used to volatility in the level of impairment charges and the profit and loss.