Launceston-headquartered Bank of us increased its loan portfolio by 21 per cent in the year to May, which was the fastest growth rate of any Australian-owned bank.

The portfolio grew by $145 million to $849 million, while the customer-owned bank's total assets grew by 18 per cent to $993 million among a series of strong 2018-19 growth numbers chairman Stephen Brown described as phenomenal.

The bank added a record 3840 new customers during the financial year, which was an increase of 29 per cent on the previous year's growth.

That took total customers to 30,000.

The bank said its market share of owner-occupied housing finance increased by 30 per cent, leading to a record $279 million of loan approvals.

"We've recorded an after-tax profit of $2.3 million, up over 40 per cent due to increased revenue from strong loan book growth," Mr Brown said.

"And financially we are performing well, with strong levels of regulatory capital and liquidity."

The bank reported a low level of arrears of 0.33 per cent as at June 30.

"This year, we implemented a new electronic loan processing system, enabling us to handle 30 per cent more loans with no additional resources ...," chief executive Paul Ranson said.

He said Bank of us was Australia's oldest customer-owned banking institution.

"Our original purpose was to provide housing finance to Tasmanians so they could build their own homes," Mr Ranson said.

"We're now in the enviable place of being able to hold true to our original purpose and deliver a full range of competitive banking products and services."

The bank will celebrate its 150^th anniversary next year.

Three foreign-owned banks had higher rates of mortgage lending growth than Bank of us in the year to May.

Tasmanian-headquartered MyState Bank was the fifth-fastest growing Australian-owned bank.