Debbie Sanich thought she had her rental car all figured out. Like many travelers, she passed on the collision damage waiver (CDW) at the rental counter. Why pay $30 to $45 a day when her own car insurance promised full coverage, right?

Last year, during a Hawaiian getaway on the Big Island, Sanich found out that “full coverage” has its limits. Another driver pulled out in front of her Avis rental, causing a minor fender bender. The other driver’s insurance paid for the damage. Case closed…or so she thought.

Weeks later, a surprise $1,256 rental car bill from Avis crashed her island vibe

Despite not being at fault, Sanich was now on the hook for fees her own insurance wouldn’t touch: $300 for administrative costs, $564 for loss of use while the vehicle sat in the shop, and $392 for something called “diminished value.” This is the amount Avis claims the car’s worth dropped after the accident.

“This was a fender bender,” Sanich said. “What if somebody wiped out the whole side of the car?”

She took her case to KSL TV, and while Avis wouldn’t budge, insurance expert Brent Thurman explained why: most auto policies don’t cover those specific charges. Essentially, your insurance might fix the rental car, but they won’t cover the money Avis says they could’ve made, or what the car’s now theoretically worth. And those charges are apparently listed in the agreement that the customer signs.

Sanich ended up paying the bill. Still, she’s saved money over the years by skipping CDWs. She says this was just the one time it didn’t work out.

The takeaway? Don’t assume. Check your car insurance. Read your credit card’s rental benefits. And if in doubt? That pricey CDW might just buy you peace of mind…and a smoother return at the rental car counter.