[stevesimmons]

The reason for that is the car rental company does a "pre-auth" that ties up some of your credit limit (reduces your "open to buy" amount), in case you damage the car or don't return it with a full tank of petrol.

Hotels will sometimes do the same for a room night plus potential minibar charges.

The pre-auth gets released when you make the payment at the end of the car rental period.

[AnssiH]

"Pre-auth" works the same way for VISA/MC debit and VISA/MC credit.

The amount is (temporarily) deducted from my available balance when I use a debit card, just like it is deducted from the credit limit when I use a credit card.