Jacinda Ardern is making it mandatory for all businesses opening under the new Alert Levels to display the Government's COVID TRACER app QR code.
Businesses have one week to display the QR code at its entry points, however the prime minister urged businesses to download the app as soon as possible.
It comes as four new community transmitted cases of Covid-19 forced Aucklanders back into Alert Level 3 at midday, and the rest of the country is in Alert Level 2.
From midday today, a Covid-19 public health order came into effect which provides the legal basis to require people to stay at home unless they are working in places where it is safe to do so, including to ensure physical distancing.
"The order makes it mandatory for any business or service to display a QR code for the COVID TRACER app prominently at all entry points, allowing everyone to sign in via the tracing app. So what is mandatory is the display of that QR code," Ms Ardern said.
"Many businesses, as you'll note, have done that already because as you'll see them on display."
The app allows users to scan the code and keep a log of where they have been. People are also notified through the app if they have been in contact with a Covid-19 case.
"The ability to contact trace quickly is one of the key tools we have to find new cases and get them in isolation to avoid future lockdowns, so always using the app is a big investment in keeping our businesses and economy open," Ms Ardern said.
"It will protect you and it will protect the people around you.
"It is very quick and it is very easy to use.
Last night, more than 100,000 people downloaded the app.