ASB chief executive Barbara Chapman will step down from the job next year.

The bank has started to look for a new boss and said that Chapman, who has been in the top job since 2011, will leave at Easter next year.

Chapman said the role has been the highlight of her career.

"I shall always be proud of what we have achieved... it has been a privilege to work with such passionate people over the years and I will continue to watch their careers with interest. ASB is set on a strong course for the future as we continue our focus on digital transformation, customer service and fostering a culture of collaboration across the bank. In terms of my own future, I am just excited to be able to take some time to think about areas of future interest and challenge."

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ASB chairman Gavin Walker said Chapman would leave a lasting legacy at ASB.

"Barbara's decision to retire caps a remarkable career of continuous service to ASB and the Commonwealth Bank Group more broadly. She has been a passionate and effective chief executive for ASB and its people, successfully leading the organisation through a period of unprecedented change and market disruption," Walker said.

"During her tenure, ASB has continued to transform into a digitally-focused organisation with a renewed commitment to delivering unbeatable customer experiences across all its channels. She has played a key role in growing ASB's annual profits from $568 million in 2011 to more than $1 billion in the most recent financial year-end," Walker said.

Commonwealth Bank of Australia's New Zealand earnings in the year to June 30 were boosted by a 13 per cent gain in ASB Bank's cash profit, as the Kiwi lender benefited from smaller charges on bad debt and stripped out costs to keep on top of shrinking interest margins.

ASB's cash profit, lenders' favoured earnings measure, rose to $1.03b from $914m a year earlier. Net profit, which includes unrealised movements in the value of financial instruments, jumped 17 per cent to $1.07b.