I thought chipping was stones flying up off the road However it now seems it refers to the engine management, I have no wish to change it, but wonder when changed what it means, and if you bought a second hand car how would you know if it had been done. My son pays over £100 road tax, and my wife pays £30 for a car with same body and same engine his has 4 wheel drive and the engine is configured to give out more power, no change in any mechanical parts on engine, only the chip in the engine management is different, car is a Jaguar XE. So I suppose if we were to fit sons chip in wife car it would be fraud? We would be paying the government less than it was due, also insurance would not be valid as the car would no longer be road legal until re-registered and paying higher rate of tax, even if we told the insurance it had been re-chipped. It seems common for caravan owners to re-chip cars to get extra power for towing, seems a little pointless as the towing limit is set my manufacturer and that would not change, with wife's car the towing limit is higher for automatic version to manual version, I would assume hill climbing ability! So even changing wheel sizes could affect towing ability. But wheel size is easy to see, adding a turbo, or other physical charge again easy to see, but changing the chip, there is nothing the user can see, and likely would only be found if involved in an accident, at which point it's a little late, so how can one be sure the car is road legal?