Census organisers say not everyone will be able to take part on March 6

It's just four days until the census and organisers admit some people won't be able to take part by then.

Some online access codes haven't arrived, and those who want the paper forms instead will face a further wait for them to posted.

Census organisers say 80 percent of households should have already received a letter but around 20 percent are left to the last minute if they live in an area of high growth, communities with lots of holiday homes or if the post was affected by Cyclone Gita.

Head of the 2018 Census Denise MacGregor says "most" people will have their letter by Tuesday.

That date might still be unknown to some as moves to on-demand TV viewing mean they've missed the ads - especially within the migrant community where English is not their first language.

While information on how to fill in the form and multi-lingual call centre workers are provided, only in the last few days has a migrant service group been asked to help translate the form itself. 

Shoma Prasad from Auckland Regional Migrant Services said "It needs to be simplified as well as multi-lingual which they are trying to do now, so they are trying to make it a bit more accessible - it might just be cutting it a bit too close."

If you are still waiting for your access code, you need a new one or paper forms sent out and you don't receive them by Tuesday - it is still possible to fill in your census in the week following - and after that, field officers will make personal calls to households that still haven't responded.

The census is designed to be a 'snapshot' of where people are on Tuesday night - but for places with transient guests like a backpackers, it's more of a challenge to achieve.

Newshub called 20 hostels but only one had received any paperwork.

Donna Goodmans from Point Break Backpackers said "I've found it quite confusing because I've got all my paperwork but what am I going to do for all my travellers that are here? Because they have to be accounted for too."

Census organisers have already counted more than half a million early responses and say despite the shift to a digital focus, the elderly are well represented in that number so far.