What happens if I don't renew my domain name?

NZ Domains

When a domain expires it is no longer visible on the Internet, however it can be reactivated with a renewal for a period of 10 days, after which the domain name is made available again for others to register.

International Domains

If the domain name has not been renewed by the expiration date, the domain name registration will move to "Lock" status, where the domain cannot be edited, for five days and then "Deactivation" status, where the domain will be dropped from the zone file and the website will no longer resolve, until the domains are deleted on the 11th day.

You may not be able to get your domain name back until it becomes free for anyone to register again.