I have never heard of this before. I have worked in the Car Rental Industry when I was younger. It was common practice for people to return their vehicle early or extend the rental. All the customer was charged was the daily rate as indicated in the rental agreement.

Now, I am surprised to read that Fox Rent A Car charges $10 + daily fee to return your vehicle early. If you extend your rental, you are dinged another $10 + daily rental fee. You are also charged for an additional driver, even if that additional driver is your spouse.

What's going on??