Final results of the MMP referendum will not be available until some time after the final election results.
While advanced votes are being counted tonight for the referendum, the remainder of votes will not be tallied until the formal election result has been confirmed.
This could mean there is no formal referendum outcome until as late as December 10.
With 94 per cent of the advance vote counted, holding on to MMP has attracted 55 per cent of the vote.
More than 150,000 voters opted to use the advanced vote system this year - an increase of 14 per cent on the 2008 election.
The 2011 referendum on the New Zealand voting system has asked voters if they wish to keep the current system of Mixed Member Proportional or if they would like to see a change of system.
They were also asked to indicate which of four possible alternatives - first past the post, single transferable vote, supplementary member or preferential voting - they prefer.
Should a majority vote for change, a runoff between MMP and the most favoured alternative may be held in 2014, but only if the next Parliament decides to proceed on that course.
If the majority of voters opt to keep MMP, a review of how the system works will be conducted by an independent electoral panel.
- © Fairfax NZ News