It doesn't quite work like that for a dealership. For an individual to tax and register a car, you need insurance (and MoT if applicable) but for a dealership, they don't need to do that. They register directly with the DVLA online services and do a similar thing with tax discs and write out their own discs. You'll find girls in the admin office have a locked cupboard with a tonne of unwritten tax discs in and they just use one of those
