Hi there,
The answer above is not completely accurate.
Domains are registered for a year at a time and cannot be edited once they are registered. The only way to change a custom domain is to replace it with a new domain.
If you still keep the old domain on the site with the new domain we will automatically redirect your traffic to the new domain, so you won’t need a separate redirect upgrade. If you cancel the old domain you’ll have no control over it any more, so you won’t be able to add a redirect.
Let me know if you still need help with this.
@keithlock75
The Site Redirect upgrade is intended to redirect traffic from one WordPress.com site to a completely different site, or or off WordPress.com. It is not used to direct traffic from one domain to another domain on the same site – setting the primary domain on a site does that automatically.
A site redirect cannot be added to a deleted site or to a cancelled domain.