FYI the % is how much light is let through
For front windows, yes, but rear windows can be black as long as you have 2 wing mirrors, which is a legal requirement anyway, as its no different to driving a van.
Vehicles first used on 1 April 1985 or later
The front windscreen must let at least 75% of light through and the front side windows must let at least 70% of light through.
Vehicles first used before 1 April 1985
The front windscreen and front side windows must both let at least 70% of light through.
And the common misconseption from here is that people think they can have 30% tint on the front. When in fact they cannot as glass has a tint to it anyway. Something like 7-11%. Friend got pulled with 15% tint on the front door windows. Which was still illegal. Not worth it.