From the MTO website;
Q16: How do I determine registered gross weights for trucks towing trailers?
The registered gross weight (RGW) determines the fee paid for commercial licence plates (black and white). The truck's RGW is based on and must be at least equal to the actual weight of the truck, or the truck, trailer(s) and load(s).
1. Weigh the truck only, with the trailer attached.
2. Weigh the trailer only, with the trailer attached to the truck.
If the trailer weighs more than 2,800 kg (6,171 lb.):
- register the truck for at least the combined weight of the truck and trailer.
Not only are the fines hefty, because they are based on a minimum amount plus a surcharge per kg you are over your RGW, but you will be ordered off the road right there. If you are lucky enough that it's because of a trailer, you will only be on the hook (literally) for having the trailer towed and stored until you can up the RGW and return with proof of same.
A friend of the family got nailed this way in Georgia, had to leave the trailer there in a storage yard and drive back to Ontario to up his RGW and get an A drivers licence. His 5'er was over the 4,600 kg limit for a class G license.
