Phone the company, and ask if you should go to work in the car given the circumstances, as you are aware this would be illegal. Ask them why you haven't received the new tax disc (it could have been lost in the post). Depending on their answer, ask them what you are supposed to do now. As it would be the company's car which would be impounded and possibly destroyed, ask if they are prepared to provide you with a different car which is fully taxed. Best of luck, but personally there's no way I would drive an untaxed car.,