TSB made a record profit of $51.2 million in the year to the end of March - up almost 20% on the previous year.
Chief executive Kevin Murphy says deposits grew more than 15% to $4 billion during the year, and the bank attracted more customers to boost market share.
"Surprisingly our loan portfolio has grown record levels, which again probably flies in the face of what one might expect," he says.
He says the bank has maintained its level of lending and conservative approach, which he says has reaped rewards in the last 12 months.
Mr Murphy says the bank set aside $4.5 million to cover bad loans during the year - up 9% from 2009.
The bank's impairment charges are among the lowest in the sector, he says, and he expects them to fall in coming years.