Another load of bull from DVLA, if you don't declare your vehicle as SORN because you still have some tax left on it you will also have to ensure that it is insured as well otherwise guess what? yet another fine. Basically they are saying that because the car is taxed but not insured you could be tempted to drive it. More of an issue for those with historic tax where you don't have to pay for the tax but may only insure the car for six months a year.
Just thought I would let you know.