Recently I bought a pre registered car from a dealership. The car was registered on 29.9.2012 and I took delivery of it on 12.10.12. The tax disc expires on 31.8.13, which is puzzling, as one usually can only buy tax discs for 6 and 12 months and new cars usually come with 12 months tax. My daughter also had a similar experience to this with a new car (not pre reg.) that she bought. When I pointed out to the salesman that the car had only 11 months tax he put £20 worth of petrol in the tank. Is there some kind of tax fiddle going on here?