None of which changes the point that, when told that I shouldn't be on the roads because I don't pay road tax, my reply of "I have three cars and two motorbikes, I pay all the tax I need to pay" will get the attention of the average, or below average, motorists far better than all the pedantic stuff about the difference between a tax and a duty.That doesn't alter the fact that they are in error if they believe they pay 'road tax' as there is no such tax.
Better answer yet, though, is often to ask the driver whether the car is theirs or a company vehicle. I urinated all over one colleague's fire when I asked him how much road tax he paid on his company Saab.