The rules on tinted windows don’t apply to the rear windscreen or the rear passenger windows. If you add any more tint it’s likely to result in the windows failing to meet the legal requirements.
In most modern vehicles there is a slight tint added to the windows when they are made. The law requires that the windows on the vehicle allow at least: The windows that must have the right amount of tint are the front windscreen and the two windows to either side of the driver. If you have a vehicle that has heavily tinted windows at the front, you are risking prosecution by the police.
