I have a Visa credit card with a $4,000 limit. I have $1,000 used at the moment, and on their online site it says I have $2550 in remaining credit, which only adds up to $3550. What is the deal with the missing $450, and is this a common practice among credit cards?
It is common that a hold is placed. For example, some gas stations "hold" $1.00 when you swipe your card to preauthorize. Other gas stations will "hold" $100.00. For the most part, you never notice this oddity. Hotels and Car Rentals also do a similar hold.
Some banks show the "hold" amounts online and others don't. In all cases I know of, if you call up the branch, they'll be able to tell you what that difference is.
Another possibility is that they lowered your available credit without telling you.
Did you use it at some places where they block the amount. For example while renting a car, or booking a Hotel, they initial do not charge, but block the amount on card.
This will not show up as transaction.
This blocking would also be incase you have taken goods on deffered payments on card, or insurance. In this case the entire amount is set as blocked, and every month only the agreed EMI is charged.