A UDAI code (pronounced you-dye) is a unique 8-character 'password' for .nz domain names. This code allows you to transfer your domain from one domain provider to another. UDAI codes only include numbers and letters and are case-sensitive.
Some domain providers have different names for the UDAI code, such as a Registry Key, or a Transfer code. To get your UDAI code you can simply ask your domain provider, you will need to ensure that this is an 8 digit code.
If your domain is with Rocketspark, you can get your UDAI code by following this help guide: How do I transfer my domain away from Rocketspark?