The Prime Minister does not conduct significant government business via text message or private email, his office says.
A decision on whether John Key's deletion of his text messages amounts to a destruction of the country's public records is progressing.
The investigation by chief archivist Marilyn Little comes as a spotlight is put on politicians' recordkeeping by Hillary Clinton's use of private email for official business. Ms Clinton, a top contender for the 2016 Democratic nomination for US president, last week said that she used private emails out of "convenience" during her time as Secretary of State.
Officials' correspondence is considered to be US government property, and thousands of Ms Clinton's emails not deemed personal will eventually be released.
The distinction of what constitutes a personal communication will be important to Ms Little's review.
She agreed to a request from Green MP James Shaw to review recordkeeping practices for Mr Key's texts between when he first took office in 2008 and November last year.
The Prime Minister said he deleted his text messages amid controversy over his correspondence with blogger Cameron Slater, as detailed in Dirty Politics.
A spokeswoman for Mr Key said Ms Little had been advised that he does not conduct significant government business via text message.
The same was true about communications on private email, the spokeswoman told the Herald.
"No government department has advised this office of any policies or processes for the management of text messages."
Ms Little would make no comment until the findings of her review were released.
Mr Shaw has said he believes Mr Key's deletion of text messages might be in breach of the Public Records Act. He hoped Ms Little would release guidelines when her review was completed.
"The Official Information Act and the Public Records Act are kind of neutral as to the technology, and so we have asked for the chief archivist to essentially come back to us and say, 'Here's what should be happening'."
Information provided to agencies by the Ombudsman makes it clear that official information includes material held in any format.
Privacy law expert Gehan Gunasekara from the University of Auckland said there were many reasons for information not to be released under the OIA, but the medium of communication was irrelevant.
"Where there is a strong public interest, everything must be handed over."
In 2011 Foreign Minister Murray McCully's private email account was hacked. Emails later released included one from his then-parliamentary private secretary suggesting ways to help people in the region to "resist China".
A spokeswoman for Mr McCully said he did not conduct substantive government business by text message, "nor does he conduct government business via private email".