You can purchase or transfer-in multiple domain subscriptions for the same website. The process is the same as when registering the first domain for the site.
If you have more than one domain subscription attached to a site, for example petersbakery.com and peters-bakery.com, you can select one domain as the primary domain. The other attached domains will then redirect to the primary domain.
How to set it up
On the Account page in RAI, click the Subscriptions tab and scroll down to view your domain subscriptions. Click the Manage button next to the domain you wish to make the primary.
On the overlay, scroll down and tick the box Use as primary domain and click Apply.
If you have multiple Mono IP addresses
In recent years, we have made efforts to ensure that each of our partners have one, dedicated IP address where all of their Mono websites are hosted. Previously, some partners had two or more different IPs that sites could be hosted on. If you have multiple domains with various IPs on an account, the primary domain will automatically be set to the most recent IP provided to you by Mono. If you want an "older" IP to be the primary domain, make sure that the A Record for the other domains on the account point to that same IP.