Here's some info that I will try to put as simply as possible(some of it may be what others have stated):
-travel trailers and fifth wheel trailers are exempt
-if either truck or trailer has/requires yellow sticker, both truck AND trailer need yellow sticker
If you are towing the following types of trailers:
-utility, snowmobile, boat, motorcycle(I may have missed some)
the following calculation is used to determine if you need a yellow sticker on BOTH
truck and trailer.
Take the highest of the weights listed below for the truck:
-actual weight(from scaling at truck stop)
-registered weight(from registration slip)
-GVWR(usually found on sticker on door jam of vehicle)
Take the highest of the weights listed below for the trailer:
-actual weight(from scaling)
-GVWR(from manufacturer's sticker)
Add these 2 numbers together.
If the result is greater than 4500kg(10,000lbs) then a yellow sticker is required on BOTH.