If you are trading as a company you will already have a NZBN as all companies get a NZBN when incorporated (go to https://companies-register.companiesoffice.govt.nz/ and type in your company name to check the NZBN). But other trading entities such as sole traders, trusts and partnerships can apply for one as well.
A New Zealand Business Number (NZBN) is a globally unique identifier number available to all the Kiwi Businesses. NZBN will link to the most commonly asked information of the business such as trading name, website and telephone number etc. This Information is called Primary Business Data (PBD).
When a business owner enters the NZBN number on an application form for example, all other relevant fields will automatically be pre-filled using information about the business on the NZBN register. When you update your NZBN register details those doing business with you and linked to your NZBN will get a notification automatically.
The spin is that using NZBN can save time and money by helping business owners to better connect and interact with other businesses and government agencies.
If you are not trading as a company you can apply for a NZBN at https://www.nzbn.govt.nz