http://www.mto.gov.on.ca/english/safety/carseat/choose.shtml
Toddlers
A child can start riding facing forward when he or she is at least 9 kg (20 lb.).
To prevent the car seat from moving forward and causing injury in a collision, it is important to use the tether strap exactly as the manufacturer recommends. If your vehicle does not have a tether anchor in place, contact a dealership to have one installed.
To install a forward-facing car seat, fasten the tether strap, then use your body weight to tighten and fasten the seatbelt or Universal Anchorage System (UAS) strap.
Ensure that the shoulder straps are at or above the child's shoulders. Straps should be snug, with only one finger width between the strap and the child's chest. Avoid using aftermarket car seat products. They can become projectiles or may have hard or sharp surfaces that can hurt the child in a collision.
•9 to 18 kg (20-40 lb.)
•Forward-facing seat
•Use with a tether strap
Pre-school to 8 years old
The law requires booster seats for children who have outgrown a child car seat but are too small for a regular seat belt.
Booster seats are required for children under the age of eight, weighing 18 kg or more but less than 36 kg (40-80 lb.) and who stand less than 145 cm (4 feet-9 inches) tall.
A child can start using a seatbelt alone once any one of the following criteria is met:
•child turns eight years old
•child weighs 36 kg (80 lb.)
•child is 145 cm (4 feet-9 inches) tall.
Seatbelts are designed to protect adults. Booster seats raise the child up so that the adult seatbelt works more effectively. Booster seats protect against serious injury 3 ½ times better than seatbelts alone.
A lap and shoulder combination belt must be used with all booster seats. Your child's head must be supported by the top of the booster, vehicle seat or headrest. The shoulder strap must lie across the child's shoulder (not the neck or face) and middle of the chest, and the lap belt must cross low over the hips (not the stomach/abdomen). Never use seatbelt adjusters.
•Between 18 and 36 kg (40—80 lb.)
•Booster seat
•Use with lap and shoulder belt