In this day and age of computers, as well as issuing a MOT on paper to the customer; they are registered on line. So all Cars over 3 years old, get taxed at the same time as they get MOT; paid to the Garage, acting on behalf of the DVLA. Then all three ( Tax, Insurance & MOT ) are logged on line against the Cars registration.  If a Car is missing either of the three on line, against its reg, the owner is visited and Tax collected at the Door; by the person visiting them. If they can't pay, a tow truck is called and the Car is impounded for 1 month; then disposed of. If a Car is missing more than one of the three, then that's a sign ( to me ) of deliberate evasion and the owner is visited and the Car is siezed and disposed of + the owners licence is taken away for 1 year. If anybody finds a way around this, they are jailed for 1 year, lose their licence for 1 year and lose their Car permanently. You don't deal with "SCUM BAGS" by making a game of it and seeing who can play the system better......them or decent people. You either solve a problem PROPERLY by doing what's necessary and having the backbone to carry it out, or you tinker with it ,in the usual gutless manner that people do and have it drag on forever.

The first three years of Tax are added onto the price of the Car, when it's bought new, payable to the DVLA by the company selling it.