Interest rates on term deposits rose at their fastest level in nearly two years in March.
Reserve Bank data shows the average six month deposit rate rose a fifth of a percentage point last month.
Radio New Zealand's economics correspondent says that's the biggest monthly increase in nearly two years, taking deposit rates to levels last seen a year ago.
Reserve Bank records show the last time deposit rates rose as quickly, higher floating mortgage rates were close behind.
Massey University banking lecturer Clare Matthews says the pickup could be related to recent increases in mortgage approvals.
The average floating mortgage rate remained anchored at 5.9% at the end of March, the lowest for 47 years.
The upward moves in returns came despite a near record high of $106 billion held in deposits.