When selling your car on Motorway, it's best to wait before making any changes until the car has been collected and paid for. This means you must ensure that your vehicle is insured and taxed until this point. Do not jump the gun early to try and save some money, as the deal could still fall through before it's collected.  After the car has been picked up and you've received your money, you'll be able to register a 'Change of Keeper' with the DVLA. Once you do this, you should automatically get a refund for any outstanding car tax. Be prepared for this refund to take around 4-6 weeks to process.