Check your contract/Price discrepancy.
For the second time in a row now (within two months) I've arrived at my car at Hertz to discover the contract hanging off the windshield was showing a price higher than what I actually booked.
Going back to the #1 Gold desk resulted in the exact same answer being given: "any coupons are applied when you return the car"
However after asking them to "please" apply it now so I don't have issues upon return they both did it, and my total ended up being less (a few dollars) than what I had booked.
How common is this? Should unsuspecting people beware?