What Is Supplemental Liability Insurance?

What is supplemental liability insurance (SLI)?

Supplemental liability insurance, commonly abbreviated SLI, is an optional coverage sold by rental car companies that increases the amount of liability protection you have for bodily injury and property damage you cause to other people, third parties, while driving the rental car. Rental cars typically come with only a minimal, legally required level of liability coverage, which may be quite low, and SLI raises that protection to a much higher limit, often up to around one million dollars, for claims from others if you are at fault in an accident. This coverage is about protecting you from the potentially large costs of injuring someone or damaging their property, rather than protecting the rental car itself. SLI is offered at the counter for a daily fee, as one of the optional protections you can add to your rental.

How is SLI different from a damage waiver?

Supplemental liability insurance and a damage waiver protect against entirely different risks, which is a crucial distinction. A collision damage waiver or loss damage waiver protects you from paying for damage to, or theft of, the rental car itself, that is, the vehicle you are driving. Supplemental liability insurance, by contrast, protects you against claims from other people for injuries or property damage you cause them in an accident where you are at fault, covering the harm you do to others, not to your own rental car. So the damage waiver covers your car, while SLI covers the other party's injuries and property. Because they address separate risks, a rental company may offer both, and having one does not provide the protection of the other. Understanding that SLI is about liability to others helps you evaluate it against the coverage you already carry.

Do you need supplemental liability insurance?

Whether you need SLI depends on your existing liability coverage, so check what you already have before buying it. Review your personal auto insurance policy to see whether its liability coverage extends to rental cars and how high its limits are, since if you have strong liability coverage that applies to rentals, you may not need SLI. Importantly, note that credit cards that provide rental coverage typically cover only damage to the rental car, not liability to others, so a credit card usually does not replace SLI. If you have little or no auto insurance, low liability limits, or no coverage that extends to rentals, SLI can be valuable protection against a potentially large financial hit from an at-fault accident. If you already carry ample liability coverage that applies to rentals, SLI may be redundant. Weigh your existing protection against the cost and risk.

How does SLI work?

Supplemental liability insurance works by providing an additional layer of liability coverage on top of the basic protection included with the rental, raising your total liability limits for a daily fee added to your rental cost. If you are involved in an accident that is your fault and another party makes a claim for their injuries or property damage, SLI helps cover those costs up to its higher limit, reducing your out-of-pocket exposure. It generally acts alongside or in excess of the rental's minimal built-in liability. As with other rental protections, SLI has terms and exclusions, such as not covering prohibited uses of the vehicle, so you should understand its conditions. To use it, you simply accept the coverage at the counter when renting. It is designed to give you peace of mind that a serious at-fault accident will not leave you facing large liability claims with inadequate coverage.