You can apply to revoke a registered relationship.
The death of either party or the marriage of either party in the registered relationship (to each other or another person) will automatically revoke the registered relationship.
You'll need to wait 90 days after you've applied before the relationship can be revoked.
You don't automatically get a certificate when your relationship is revoked. You can choose to get one at the same time as your application, or separately afterwards (see Get a revocation certificate).
See Withdrawal of application to register or revoke a domestic relationship if you need to withdraw an application you have already submitted.