Chief Electoral officer Robert Peden said since the by-election was announced in February, more than 500 people who were not previously enrolled have done so.
While that was very pleasing there were still 4000 eligible voters in the Northland electorate not enrolled.
Mr Peden said those people had until Friday to get on the roll, if they want to vote.
"At this point in the process you really need to get a move on and the easiest way to enrol at this point would be to go to your nearest Post Shop or go to an advance voting place and complete your enrolment form there, before you vote."
Advance voting for the 28 March Northland by-election is more than double that in the electorate for last year's general election.
Eleven candidates are contesting the Northland seat:
- Adrian Paul Bonner, Independent
- Joe Carr , Focus New Zealand
- Robin Grieve, ACT New Zealand
- Maki Herbert, Aotearoa Legalise Cannabis Party
- Adam Holland, Independent
- Mark Osborne, National Party
- Rob Painting, Climate Party
- Winston Peters, New Zealand First Party
- Reuben Porter, MANA Movement
- Willow-Jean Prime, Labour Party
- Bruce Rogan, Independent