For reference, http://www.landtransport.govt.nz/factsheets/39.html
Key points:
A vehicle that has nine or fewer seating positions, including the driver's seat, has tinting restrictions for all the windows:
All other vehicles, including those used as stretch limousines or for transporting the deceased, have restrictions on the windscreen and front side windows, but can have any level of tinting film applied to the rear and side rear windows, and the back window.
There are further images (examples for Utes and Trucks, etc) at the above link.
I have not found anything that clearly indicates that a vehicle registered as a commercial has different rules to follow as relates to window tinting.
STICKERS / BANNERS
- * If the stickers are on the windscreen, they must be completely within 100 mm from the top or bottom edge of the windscreen or within 50 mm from the side edge of the windscreen.
* Stickers on the front side windows must be completely within 100 mm from the bottom edge of the glazing or within 50 mm from the top or side edges.
* If your vehicle has nine or fewer seating positions, stickers on the rear side or rear windows must be completely within 100 mm from any edge of the glazing.
