In reply to Removed Userbennett_leather:
By my reading your car is taxed and always has been. It's just it is taxed at the disabled rate of zero. If the police stop you their checks should say it is taxed (albeit at the zero rate). Simple really as far as the tax status goes.
You must have been through as many ANPR cameras over the last 14 months and if you've not had numerous letters or knocks at the door, this would strongly suggest that it is still taxed. If you are still not convinced go to
https://www.gov.uk/check-vehicle-tax enter the details and I reckon that it will say tax not due, taxed till --/--/----. In the unlikely event it says tax is due (unlikely as you would have had the warning letters already) get is sorted out now (and don't drive the car on the road until it is).
If they (DVLA/police/ANPC camera operators) look into it further the real question would be is it fraud. That is have you knowingly failed to notify the DVLA for 14 months that the vehicle is not now for use by a disabled person and so should not have continue to qualify for the zero rate (exemption from tax effectively)? From what you say there is plenty "proof" that you have notified of the change, plus you have presumably paid the DVLA for 14 (or at least the 12?) months at what should be the correct rate.
If it was me I would just get the error corrected as soon as possible, and get the "tax" already paid for the 12/14 months credited to the correct vehicle records.