Today is the last chance for people to return outstanding Census forms, Statistics New Zealand says.
Statistics NZ says from tomorrow it will begin collating the data collected from the 2013 Census.
"We will also begin the process of considering taking action against those who have not completed their census obligations," Government Statistician Geoff Bascand said.
He said anyone who was in New Zealand on March 5 was required by law to complete the form.
"So far Statistics NZ has collected well in excess of 5 million census forms (individual and dwelling forms combined) and we are now in our final few days of collecting outstanding forms."
He urged anyone who has a form sitting at home to post them immediately.
"Warning or prosecuting people for failing to complete census forms is a last resort and we would rather people voluntarily returned completed forms."
Not completing the 2013 Census could ended up costing New Zealanders thousands of dollars.
Fines of up to $500 could be handed to anyone who failed to complete the Census on March 5. With an extra $20 fine for every day the form remains uncompleted.
The information from the 2013 Census will be used to make decisions in health, education, transport and the Christchurch rebuild.
There was a big push for people to complete their forms online this year.
It is the first census in seven years, after the 2011 event was cancelled due to the Canterbury earthquakes.
The last time a census was postponed was during World War II in 1941.