The rental company.
Car rental companies offer a collision damage waiver that covers some loss or damage to the rental vehicle. It transfers the responsibility for the cost of the damage from you to the auto rental company. There are exclusions, so check the fine print. You can purchase the collision damage waiver from the rental company at a daily rate that is in addition to the rental charge. The cost for this coverage usually ranges from $25 to $27 per day.
Your credit card.
Your credit card may provide collision damage coverage on automobiles that you rent. However, there may be certain limitations or conditions. You should check with your credit card provider to learn about any restrictions.
Your current auto insurance policy.
Most Ontario auto insurance companies offer the option of additional liability coverage for damage to automobiles you don't own. The coverage is known as Legal Liability for Damage to Non-Owned Automobiles and is an endorsement that can be added to your existing policy. This endorsement is only valid for non-owned automobiles driven in Canada and the United States. If you are driving internationally, you will have to purchase coverage elsewhere. The cost for the endorsement varies, but averages between $30 and $35 per year – a substantial savings over rental company daily rates. Contact your agent or broker to add the Legal Liability for Damage to Non-Owned Automobiles to your policy. Check with your insurance agent or broker for more details. Your insurer is your best source of information.
https://www.ilolaw.ca/blogpost/rental-car-accident
Collision Damage Waiver
Regardless of the other coverages you have, it might be a good idea to purchase the rental car company's collision damage waiver on the rental car insurance policy. With this rider to the insurance policy, the renter will not be held financially responsible if the car is damaged or stolen. The downside is that such a policy waiver will usually double or triple the daily cost of your rental car. However, for many people it's better to be safe than sorry and the insurance company is betting you'll agree.