Theres already a public access database for checking tax! 
It tells you the date of registeration, the date the tax is due and how much it costs....I use it all the time when looking for cars.
https://www.gov.uk/check-vehicle-tax Go there then select vehicle enquiry from the left hand side...just put the reg and make in.
Tbh I cant see a problem with the new system, most of us probably tax online anyway....and the police already use ANPR for tax....so the only difference is the paper disc, which just creates untidiness and non-simitary on the windscreen.
It tells you the date of registeration, the date the tax is due and how much it costs....I use it all the time when looking for cars.https://www.gov.uk/check-vehicle-tax Go there then select vehicle enquiry from the left hand side...just put the reg and make in.
Tbh I cant see a problem with the new system, most of us probably tax online anyway....and the police already use ANPR for tax....so the only difference is the paper disc, which just creates untidiness and non-simitary on the windscreen.