Once you've purchased a Domain with Vercel or transferred it in from a different platform, Vercel will automatically make sure that your Domain is renewed every year – before it expires.
Like this, you never have to worry about your projects becoming unavailable. Instead, you will automatically be charged the renewal fee every year and your Domain will continue working.
Previously, the only way to prevent a Domain from being renewed again (in the case that you don't want to continue using it, for example) was contacting our Support Team, who disabled auto renewal for you.
As of today, you can toggle the auto renewal behavior of a Domain right on the Dashboard by navigating to the "Domains" tab on your Personal Account or Team, clicking the Domain you're interested in and toggling the option on the top right.
Check out the documentation as well.