The cost of a child sex offenders register is $146 million over 10 years, according to a regulatory impact statement for legislation going through parliament.
Under a bill introduced by the Government last week, all child sex offenders will have to register if they were aged 18 or over when they were convicted and sentenced.
People who were convicted and sentenced in other countries will also have to register if they're living in New Zealand or intend to.
The register won't be open to the public, but in cases where there's a "significant threat" information may be released to a parent, guardian, teacher or caregiver.
A regulatory impact statement prepared by police and the Department of Corrections recommends the register be set up and says over ten years four to 34 child sex offence convictions may be prevented, as well as the prevention of many undisclosed, or unreported child sex offences.
Of the $146m cost over ten years, $85.1m will be met from existing baselines in the corrections, police and courts budgets.
New funding of $60.92m is required.
On April 14 Cabinet approved between-budget spending contingency funding of $35.5m over ten years for the technology component of the register.
Potential sources of funding for the remaining $25.4m over 10 years are a bid to Budget 2015 and savings from expenditure reviews currently being conducted by justice sector agencies.
The Accident Compensation Corp (ACC) has indicated a willingness to provide some seed funding for the initiative, the statement says.
Child sexual abuse is a serious problem in New Zealand.
In 2012/13, 505 offenders were convicted of 1819 sex offences against children, up by more than 20 percent from a decade earlier, according to the statement.
In 2012/2013 ACC had 779 sensitive claims for sexual abuse lodged for children under the age of 16 years.
Offender registers have been implemented in a number of overseas jurisdictions and they help government agencies to identify and manage the risk of sex offending in the community, the statement says.
Risks associated with registers include human rights and privacy concerns, the cost of maintaining them, and the possibility of stigmatising offenders, which can have the effect of increasing re-offending.