Inland Revenue is hoping to reunite $55 million with its rightful owners.
Records dating back to 1973 show nearly 97,000 cases of unclaimed money. The amounts range from small sums to just over $371,000 in one case.
When institutions holding the funds are unable to find the owner, the money is handed to Inland Revenue.
In the past year, about $1.7 million has been returned to the department.
IRD has updated its website with a list of people it is having trouble tracking down.
Group manager for customer operations Heather Daly says people can change jobs, change their name or move location, including overseas, without knowing money is owing to them.
Ms Daly says the unclaimed money is from deposits in banks or other financial institutions, insurance proceeds, cheques and wages - rather than tax refunds.