Establish whether the old inbox is accessible
TVNZ’s current email-change help separates two cases. If the original inbox is still available, it directs deleting the current account and registering with the new email. If that inbox is no longer accessible, it directs creating a new account with the new address. Those are replacement-account routes, rather than a menu for editing one character in an existing account email.
Decide what saved information matters
The same help says watch history, saved progress and preferences are permanently removed on deletion and cannot be transferred to the replacement account. Before choosing that route, note any series and episode position you want to find again. This is a manual viewing aid, not a promised import method or a way to preserve the old account’s data automatically.
Use the primary profile for deletion
TVNZ’s deletion instructions require the primary profile and either the mobile app or a web browser. In Account Settings, select Want to delete your account? and confirm with the one-time code sent to the account email. Smart televisions and game consoles do not offer this deletion flow. The code step also explains why access to the original inbox matters for that branch of the process.
Treat the replacement as a fresh viewing record
The deletion help additionally names My List and profile information among the unrecoverable data. Choose deletion only when that intended scope is clear; signing out of a borrowed television is a narrower task. On the new registration, rebuild the useful selections you noted, while recognising that this does not restore the previous progress record behind the scenes.