Latest DVLA figures reveal that 111,781 cars more than 40 years-old were still registered in the Private Light Goods (PLG) class for Vehicle Excise Duty (VED), despite being old enough to qualify for the rolling tax exemption. Potentially owners have paid £35.8m in unnecessary VED according to the FBHVC and Practical Classics magazine. You can apply for tax exemption if your classic car was built before January 1st 1985.
For cars over 40 years old you don't need an MOT or insurance document (except in Northern Ireland) so even vehicles not currently on the road or undergoing restoration can apply for the change to 'Historic.'
https://www.gov.uk/h...e-tax-exemption
Basically you take the required documents to a Post Office that deals with car tax and the counter person scans the barcode on your V5 (signed, dated and with 'Historic' entered in changes section), checks your MOT exemption V112 form, gives you a printed receipt with reg number and taxed £0.00 and sends off the V5 to the DVLA for you. A few days later the Car Tax website should show your vehicle as now taxed. A few weeks later you should get a new V5c in the post with Historic as tax class. A few weeks later you may get another letter saying your vehicle is showing as taxed but not insured on the Insurance Database at which point you must either insure the vehicle or declare SORN.
There have been reports that changing any other details on the V5 at the same time, especially keepers address can complicate things and even result in a vehicle inspection being required.....so as always with the DVLA keep it simple and do one change at a time!