Never heard of this before. If your cover note really is just that, and has your name and details, plus the details of your car, plus the name of your insurer on it, then that it all you should need to get a tax disc. Try a different post office! You should not need to produce the schedule, in fact on the tax form it actually says that the schedule is not a substitute for the certificate, but it does state that a cover note will be acceptable. I doubt that you would get let off by the police if caught without a tax disc, they wont be interested in your excuses, they will just see a car being used without a disc, and will act acordingly! By the way, you have to have a tax disc or declared 'statutary off-road notification' (SORN) certificate these days or the DVLA will just issue a summons in the post, without the police needing to ever 'catch' you without a tax disc! beware!