Further to my previous response, I've discussed this with my Motor Trade Team who inform me that Insurers generally wont allow NCB from M/Trade policies to be transferred to Private Motor Policies, but where traders are ceasing to trade and reverting back to private policies they usually obtain a Claim Free Driving letter from the M/Trade insurers to confirm the number of claim free years they have had. Generally they find that most private motor insurers will accept this.