Adding a new vehicle to your existing account:
To add a new vehicle to your existing SiriusXM service, write down the radio ID or VIN for your new radio, then call Customer Care at 1-888-539-7474. You can also manage your account online here or register here.

Transfer paid subscription to a new vehicle:
If you've traded in a vehicle for a new purchase or lease, any unused portion of your current subscription can be transferred to your new ride* by calling 1-888-539-7474.  You can also transfer your service online; log in here to complete a transfer of your service through online account management. If you do not already have an online account you will need to register first.

The transferred trial has no cash value and can only be used toward service.  

* some exceptions apply