It is not necessary to verify the identity of an OIA () requester (unless they are a NZ body corporate requesting personal information about the requester (s25)) and they do not have to provide personal details. However, if you have concerns about the nature of the information sought and whether they meet the section 12 requirements of a person entitled to make a request (i.e. NZ citizen/permanent resident/in NZ), you may ask for a reasonable level of evidence, e.g. a NZ address or phone number, but you cannot demand proof of identity.
[Emphasis added]
The Ombudsman has said it is fine for agencies to ask for proof of eligibility where they have real concerns about it, and the police guidance on that seems OK (what's not OK is that they repeatedly ignore it, demanding photo ID rather than just an address or phone number). But the first bit, which purports to permit an ID check based on what is requested, is flat-out unlawful. That is simply not something permitted under the Act, and it makes it clear that the true purpose of such demands is almost always to discourage requests the police don't like.
The Ombudsman should stomp on this, and a law-abiding agency would obey them and change their behaviour. But we've seen repeatedly that the police care as little for the Ombudsman's legally binding "recommendations" as they do for the IPCA's. Which highlights firstly, a need for criminal penalties for non-compliance with the Act, and more importantly, a need to get rid of the eligibility requirement entirely (as recommended by the Law Commission) to prevent this sort of abuse. And if any MP wants to take some steps on the latter, there's a bill you can put in the ballot here.