tax disc 
noun British
A circular label displayed on the windscreen of a motor vehicle, certifying payment of road tax.And if you were caught without having a current tax disc decorating your windscreen, the Borough Council web site will enable you to make atonement for your sin to the tune of E60....
- Charges of using a fraudulent tax disc, fraudulent registration mark, no test certificate and no insurance on the same date were also included.
- Basically, I bought a stolen tax disc and a stolen MoT certificate, put them in my vehicle, got stopped by the police and then produced them.