Steady falls in charges for bad and doubtful debts have been a significant contributor to banks' profit growth over the past few years. However, last week's bank results suggest that the cycle of improving bad debt levels may have ended.Analysts' reports on Commonwealth Bank's, Bendigo and Adelaide's and Suncorp's results indicate that there is debate on this issue, with some analysts arguing that the cycle has turned while others see the continuation of a benign credit environment.Commonwealth Bank booked A$953 million in loan impairment expenses in the year to June - down 12 per cent on the previous corresponding period. However, the impairment charge in the June half was up nine per cent on the December half. The bank said the second half increase was due to four of the bank's bigger accounts in the business and private banking division.The bank said they were all long-standing credits and the circumstances were not correlated. It insisted there was no evidence of systemic weakness.The bank also pointed out that small and medium businesses were still deleveraging and that credit quality metrics were all sound.Bendigo and Adelaide Bank's bad debt charge rose from $69.9 million in 2012/13 to $81.9 million in the year to June - an increase of 17.2 per cent.The bank said it had a construction industry exposure that had a significant impact. It said northern Australia cattle property values, where it has agribusiness exposures, stabilised during he year.Suncorp Bank's bad debt charge fell 66.9 per cent from $375 million to $124 million for the year to June. However, as a result of drought in Queensland and parts of New South Wales, impaired agribusiness loans grew from $139 million in 2012/13 to $208 million in the year to June.In a note on the CBA result, Credit Suisse said the decline in bad debt charges might have run its course. It noted that all of CBA's operating divisions saw a rise in bad debts in the second half, except for retail banking services.In its commentary UBS said CBA had "acknowledged" that bad debt charges were unlikely to go lower than current levels. However, its view is that asset quality "remains very strong", with gross impaired assets as a proportion of gross loans down from 67 basis points to 55 bps.Macquarie Securities said: "Despite the uptick we expect impairment expense to remain benign on 2014/14."