A strong economy has helped boost the Bank of New Zealand's half-year profit by 7 per cent to $709 million.

The bank's total operating income rose 7.1 per cent in the six months to March 31 to hit $1.498 billion.

While it also kept a tight rein on expenses which fell 2.2 per cent to $489m.

Chief executive Dan Huggins said the bank had worked hard to support its customers to invest in their homes and businesses.

"New Zealand's resilience and success can be seen in our results."

BNZ's total lending grew 7.8 per cent on the prior comparable period supported by strong home loan growth while its deposits and other borrowings increased 9.1 per cent.

Huggins said while there was uncertainty ahead the bank also saw opportunity.

"We'll continue to be flexible and supportive and find ways to make banking easy for our customers."

The bank also recorded a credit impairment charge of $21m compared to the $17m write-back in the March 2021 first half.

Its cash earnings were up 8.4 per cent to $668m.

The bank's KiwiSaver business also grew strongly rising 23 per cent or $800m over the period.