By RNZ

New Zealanders should expect delays in receiving their mail and parcels as most of the country moves to alert level 3 on Tuesday night, New Zealand Post warns.

NZ Post chief customer officer Bryan Dobson said the snap change to level 4 meant a decline in parcels going through the network but volumes are back to normal and they are asking people to be kind and patient as deliveries may be delayed.

At level 4, post is restricted to essential items, with the Government providing businesses and consumers guidelines to what is deemed essential, and what isn't.

"Our role is not to police or to stop the items that come into our network, effectively our customers need to work out whether they can operate at level 4 and can comply with the various rules around that. It's not practical or possible for NZ Post to determine what's in a parcel or container of parcels and whether that's essential or not.

"We've been talking particularly with our larger senders late last week and with some of the uncertainty as we go into level 3 we want to avoid a big spike of parcels coming into our network so as we head in level 3 we'll be working with them to manage the amount of parcels that we pick up every day so our network can flow."

The organisation was planning for more capacity over the next week, and would accept items from its larger senders once it could take on increased volumes.

"We do have the additional complexity from Wednesday where we effectively have a level 3/ level 4 border. I think the rules are reasonably clear that within level 4 only essential businesses can operate but I know our customers have had some questions around parcels going across that border and what it means," Dobson said.

It had sought clarity from the Ministry of Business, Innovation and Employment.

"We are asking people to be kind and patient at the moment and have some patience that things might just take a little bit longer as we move into level 3."