The Electoral Commission says hundreds of votes at three booths were wrongly allocated to fringe parties.
Party votes were recorded incorrectly at two voting places in Port Waikato and one in the Christchurch electorate of Ilam, it said.
Most were incorrectly assigned to the Leighton Baker Party or the New Conservatives instead of the National Party.
A small number of votes were also affected, that had been cast for Labour, Greens, NZ First, Te Pāti Māori and some of the small parties that did not reach Parliament.
Chief Electoral Officer Karl Le Quesne said the mistake did not not affect the overall results.
"We apologise that these data entry errors were not picked up in the checks made before the official results were published. They should have been corrected and we regret that didn't happen," Le Quesne said.
"A full check of all voting place results is being undertaken immediately to establish if there are any other transcription errors."
The Electoral Commission's acting board chairperson Jane Meares said she had full confidence in the integrity of the election process and the results.
"A large amount of data needs to be entered to produce the results for a general election, and some mistakes due to human error can occur. However, the Board will commission an independent review of the quality assurance processes in place."
The certificates for the results would be updated and signed by the Returning Office (Electorate Manager) and a Justice of the Peace. The amended declaration of the results will be published on [www.electionresults.govt.nz the election results website] and in the New Zealand Gazette.
A full list of the changes, provided by the Electoral Commission, can be found here.