In Ontario, children must use a booster seat if they are under 8 years old, weigh between 18 kg and 36 kg (40–80 lbs), and are less than 145 cm (4'9") tall. The booster seat helps position the adult seatbelt correctly over the child's chest and hips for maximum safety. Failing to follow these laws…
From the food they eat to the air they breathe, protecting children from harm is of the utmost importance to all parents and caregivers. Yet, among all the precautions we take daily, one often-overlooked risk lies in the very activity that’s a part of most families’ routines—driving. Sadly, motor vehicle accidents remain a leading cause of injury and death for children across Canada. According to the most recent statistics, more than 700 children are killed in car collisions each year in Canada, and over 50,000 are injured—many of these injuries could have been prevented with proper car seat and booster seat use.
Despite advances in vehicle safety technology, child restraints continue to be the most effective measure to reduce injury and save lives. Parents and guardians must be fully aware of and compliant with Ontario’s booster seat laws to ensure their children's safety in vehicles. In this guide, we’ll walk through these laws, how to select and install the right booster or car seat, and what to do if your child is injured in an accident—either caused by you or someone else.
Booster seats play a critical role in ensuring the safety of children in vehicles. They elevate a child to allow the adult seatbelt to fit correctly across the strongest parts of their body—the chest and pelvis—rather than vulnerable areas like the neck or stomach. This seemingly simple function can make a life-saving difference. According to Transport Canada, children in booster seats are 3.5 times safer than those using seatbelts alone.
Ontario’s laws are strict for good reason. The Highway Traffic Act mandates that children who meet all of the following criteria must use a booster seat:
Weigh between 18kg and 36kg (40 to 80 lbs)
Are under the age of 8
Are less than 145 cm (4 ft 9 in) tall
As long as your child remains within these limits and is too large for a forward-facing child car seat (as defined by the manufacturer’s instructions), Ontario law requires the use of a booster seat. These regulations are backed by years of research and crash-test data that prove their effectiveness in protecting children during collisions.
How Long Does A Child Need to Be in A Booster Seat?
The amount of time a child must use a booster seat depends on their age, weight, and height. As per Ontario car seat laws, your child can stop using a booster seat when at least one of the following is true:
The child is 8 years old or older
The child weighs 36kg (80 lbs) or more
The child stands 145 cm (4 ft 9 in) or taller
That said, even if your child meets one of these requirements, it may still be safest to keep them in a booster seat until the adult seatbelt fits properly—more on that in the next section.
When Can A Child Sit without A Booster Seat in Ontario?
While legal guidelines provide minimums, parents should also consider practical fit and comfort. A child is truly ready to ride without a booster when they can sit all the way back in the vehicle seat with knees naturally bending over the seat edge, and when the seatbelt fits them correctly.
Here’s what proper seatbelt fit looks like:
The shoulder belt lies flat across the middle of the chest and shoulder—not the neck or face.
The lap belt rests snugly across the upper thighs or hips—not the stomach.
Children who don’t meet these fit criteria are at risk of serious internal injuries in a crash. Keep in mind, some kids won’t fit a seatbelt properly until age 10 to 12. Safety always comes before convenience.
How to Select The Best Booster or Car Seat for My Child
As we've seen, using the correct booster or car seat for your child is not just the law. It can be a matter of life and death. Let's look at how to choose the best seat for each age group. Regardless of whether you are buying a booster seat or car seat, the symbol to look for is called the National Safety Mark, and it looks like this:
Infants (Birth to 9kg or 20 lbs)
Infants must ride in rear-facing car seats. This position offers maximum support for their head, neck, and spine in the event of a crash. Experts recommend keeping infants rear-facing as long as possible, ideally until they outgrow the height or weight limits set by the manufacturer. Many rear-facing seats in 2025 are now designed to support babies up to 35 lbs or more.
Toddlers (9kg to 18kg or 20–40 lbs)
Once your child reaches at least 20 lbs, you can transition them to a forward-facing car seat with a five-point harness. However, they should remain in a rear-facing seat until they’ve truly outgrown it, because it's the safest position. When you make the switch, ensure the forward-facing seat is properly installed and use the tether strap, which greatly improves safety in a frontal crash.
Pre-School to 8 Years of Age
Children who are at least 40 lbs (18kg) can move into a booster seat. Ontario law mandates that children stay in booster seats until they are at least 8 years old, weigh 36 kg (80 lbs), or are 145 cm tall (4’9”). It's advisable to keep your child in the booster seat until they meet all three criteria for maximum safety. Be sure to check the booster seat’s manual and expiry date to ensure it’s still safe and effective.
How to Install A Booster Seat
Booster seats vary slightly from model to model, so it's always good to follow the manufacturer's instructions. Booster seats should be installed in the backseat only for safety. They should also be installed with shoulder belts, not just lap belts.
That said, the basic principle in most models is that the belt clips onto the side of the seat. Once the child is in place, the belt then acts as a lap belt and shoulder belt.
Some come with additional safety features, such as latches that can be anchored to the car.
Should I Ask The Store to Install It?
Many retailers now offer in-store installation services or workshops led by certified child passenger safety technicians. If this service is available, it’s highly recommended. If not, ask for a demonstration or instructional booklet.
Do High Back Boosters Need to Be Installed?
High-back booster seats typically don’t use a latch system but are placed on the vehicle’s seat and used with the car’s seatbelt system. Some high-back boosters come with added side-impact protection and headrests, which are especially useful for vehicles with low seatbacks or no headrests.
What Are the Height and Weight Requirements for a Backless Booster?
As of 2025, children must be at least 40 lbs (18 kg) to safely use a backless booster seat. This change reflects growing research showing that smaller children are better protected in a 5-point harness system. If your child is close to the minimum weight, a high-back booster may offer better overall protection and positioning.
Can The Police or Fire Departments Help Me to Install It Correctly?
Yes. Many Ontario communities offer free car seat inspection clinics through fire departments, police stations, or public health units. These professionals can assess the fit and installation and help correct any mistakes—many of which are surprisingly common.
Understanding Booster Seat Laws in Ontario
As your child progresses from using a booster seat to a regular seat belt, you know what their next question will be: When can I sit up front?
It may surprise you but there is no local law on this point, either in terms of age or weight. However, the Ontario Ministry of Transportation recommends that children under 13 do not sit in the passenger seat. This is because they are away from active airbags, which can pose a danger to them in the event of an accident.
The Importance of Expiry Dates on Booster Seats
Unlike diamonds, booster seats are not forever. They all come with an expiry date and it's there for a reason.
Over time, plastics degrade and do not offer the same level of protection as when they were first manufactured. Also, car seats are made in line with current laws which are updated continually. Recalls and limitations in manufacturer testing also mean a newer seat is safest.
While a second-hand seat may be a bargain, also take into consideration that kids put car seats through a lot of wear and tear. Always bear in mind, this is primarily a safety device.
While you may not be breaking the law in using an expired car seat, it's not the safest route. Additionally, if you try to sell a car seat made before January 1, 2012, this may be illegal.
What If I Am Caught without The Correct Booster Seat for My Child?
If you are caught breaking the car seat regulations mentioned above, you will be fined and receive demerit points on your license. Previously, this stood at $240 and 2 demerit points if convicted. Recent research however, shows us that those fines have now been increased to upwards of $1000 per child under 16 without correct booster, car seat, or seat belt.
What If My Child Is Injured in An Accident That I Caused?
If the worst happens, and your child is injured, your first thoughts will be seeking medical help for your child and dealing with the emotional aftermath.
From a legal standpoint, depending on the circumstances, this may be investigated as a criminal infraction of the Highway Traffic Act. If an infraction such as criminal negligence was proven, you could be prosecuted.
What If My Child Is Injured in An Accident That Someone Else Caused?
As above, an investigation may explore the possibility of criminal charges. If they have third-party insurance, you will be entitled to claim against this for any injuries suffered. Also, as a private individual, you may be able to pursue this under Canada's liability laws.
In Ontario, a child can legally stop using a booster seat once they are 8 years old, weigh at least 36 kg (80 lbs), or are 145 cm (4'9") tall—whichever comes first. However, it is safest to keep a child in a booster seat until they meet all three criteria to ensure the adult seatbelt fits properly.
While it's not illegal for a 7-year-old to sit in the front seat in Ontario, it is strongly discouraged. The safest place for children under 13 years old is the back seat, away from active airbags. Airbags can cause serious injury to young children, even when they are in a booster seat.
If a child is not properly secured in a booster or car seat, the driver can face a $240 fine and two demerit points under the Ontario Highway Traffic Act. More importantly, improper restraint puts the child's life at serious risk in the event of a collision.
Yes, Ontario law permits the use of backless booster seats as long as the child is at least 18 kg (40 lbs) and fits the seat properly. However, high-back boosters are recommended for younger or smaller children, or if your vehicle lacks proper headrests or side-impact protection.
Yes, booster seats do expire, typically 6–10 years after the manufacture date. While it may not be explicitly illegal to use an expired booster seat, doing so is highly unsafe and could affect insurance claims or legal outcomes if your child is injured in a crash. Always check the expiration label on the seat.
Conclusion
Booster seat laws in Ontario are great protection - both for parents and children. They help ensure that you can get from A to B, with minimal drama in between.
Whether you’re a new parent or just refreshing your knowledge, understanding and applying these rules is one of the most important things you can do to protect your child. Always follow age, weight, and height recommendations, check for expiry dates, and seek help with installation if you’re unsure. Their life is worth it.
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