You were expecting a simple answer, weren’t you? The truth is, there is no guarantee you are covered simply by having collision coverage and a comprehensive policy if you happen to damage a rental car.

So a more appropriate bit of advice would be to always ask. Ask your insurance provider, ask your credit card company (if that’s how you are planning to pay for the car), and ask the rental car company.

But here are a few things you need to know when considering renting a car.

First, if you have collision and comprehensive coverage, you are most likely covered for the damage to the vehicle. But what is more uncertain is the “loss-of-use” charge incurred when a rental product is out of commission. To understand this fee, think of a rental DVD. You could buy that DVD at any store, new, for probably under $20, but to a company that rents that DVD, it’s potentially worth a couple hundred dollars. Car rentals work the same way. When a car is in the shop, even though it’s being fixed, the amount of money lost because no one is renting it can pile up. Your policies may not cover this—so ask your provider.

Second, each state has its own rule about the “loss-of-use” rule. So it also matters where you are renting the car. Ask the car rental company about this. They should be able to help you out.

And finally, it might be worth it to buy rental insurance simply to avoid filing a claim with your insurance provider in the event of an accident. Your premiums shouldn’t increase as much if your car insurance agent doesn’t have to foot the bill.