In general, no.
If you already have a Paramount+ account and are presented with a prompt to transfer your SHOWTIME account information to Paramount+, do not agree to the transfer because you may end up having two Paramount+ subscriptions at the same time. Instead, cancel your SHOWTIME subscription and then log into Paramount+ with your existing Paramount+ credentials and confirm if you already subscribe to the Paramount+ with SHOWTIME plan or if you need to upgrade or reactivate your Paramount+ subscription.
If you previously subscribed to the Paramount+ Premium plan or a Paramount+ and SHOWTIME bundle, and your subscription is still active, you may already have access to the Paramount+ with SHOWTIME plan, and you should cancel any existing SHOWTIME subscription.
If you previously subscribed to the Paramount+ Essential plan or you no longer have an active subscription, you can upgrade or resubscribe to the Paramount+ with SHOWTIME plan at any time through your Account Settings. For information on upgrading your plan, click here.