NEVER use a car seat that does not have the CMVSS (Canada Motor Vehicle Safety Standards) Sticker on it.
Canadian car seat safety standards are very high. Using a car seat from the United States or any other country, increases the risk of injurt to your child and could lead to fines and/or demerit points should you be stopped by the police.
If you have been in an accident, even if it was a minor "fender bender", you must replace your car seats. There is no way to know what stress damage your car seats may have sustained. Most insurance companies will cover the cost of replacement, or at least a substantial portion of cost
DO NOT change your child to a forward facing position until the child is AT LEAST one year old and 22 lbs. Studies have shown a substantial increase in safety when they are rear facing. In fact, the latest policy statement from the American Academy of Pediatrics (April, 2011) states, "All infants and toddlers should ride in a rear-facing car safety seat (CSS) until they are 2 years of age or until they reach the highest weight or height allowed by the manufacturer of their CSS."
Forward facing seats with a 5 point harness until the child is at least 4 years old, 40 pounds, and 40 inches tall. Moving to a booster too soon is a SERIOUS RISK for injury and their safety, in the event of an accident.
Always check the date of manufacture on your car seats. Because of heat and cold, the plastics in your car seat can age. That is why all car seats have an expiration date. Click here for more information
And never buy a used car seat. You do not the history of it. Has it been in an accident? is it expired? Or is it just plain gnarly?