The short answer is yes you can.
If you already use Receipt Bank independently, you can easily Grant access to us from the Account details tab under the Account settings menu. You will find the Grant access button there, which needs to be hit and our details added.
Simply send the invitation to: email@example.com
Once that is done, an invitation will be sent to us. We'll accept it, the client will be added to our account and Receipt Bank will have transferred your subscription to us.