ANZ's provision for credit impairment in the six months to March was A$538 million - 20 per cent lower than the $675 million of impairment provisions in the March half last year.However, individual provisions went up from $609 million to $717 million, an increase of 17.7 per cent year-on-year. Total provisions fell as a result of the bank releasing $152 million from its collective provision.Total provision as a percentage of average net advances fell from 0.35 per cent to 0.27 per cent.ANZ chief financial officer Peter Marriott said: "We had a number of exposures that were not specific, so we added to our overlay in the previous half. "A number of those have crystallised and individual provisions have gone up. The corresponding collective provision has been released. The collective provision did what the collective provision should do."One of the individual charges is understood to relate to ANZ's role as merchant acquirer for the failed airline, Air Australia.Net impaired assets fell 19 per cent to $3.6 billion. Total net loans and advances were $412.6 billion - up nine per cent year-on-year and four per cent half-on-half. Marriott said new impaired assets were up from $1.8 billion in September to $2.3 billion in March. The increase all came from the institutional division and included "two large single names".Marriott said that "in general" impaired assets were improving.There was a "slight uptick" in mortgage arrears at higher loan-to-valuation ratios and an increase in the number of middle-market corporates on its watchlist. The corporates were in industries that have been adversely affected by the high Australian dollar.Marriott said the provision for credit impairment for the full year would be in line with the 2011 result.