I have decided to trade my 7-year-old Vauxhall in for a new one. I am collecting my new car tomorrow. I still have five months left to run on my tax disc. Am I expected to leave it in the car? The price for my new car was advertised on the web, so the tax disc should make no difference to price as I have to pay for the new tax disc on the car. I need to submit the refund form tomorrow so as not to lose a whole month's refund.