In some cases it is still possible to go over a card limit through the way transaction processing works. For instance, when you go to a restaurant and pay in the US they will run the card for the amount of the bill (which may not decline because you have enough $), but you might add a tip on the receipt. The tip will be added to the final charge and taken from your account, potentially making you over the limit. This is usually never stopped but might cause you fees and banking headaches. They may implement a similar procedure like gas stations usually do, by pre-authorizing a fixed dollar amount such as $50 or $100 and sending through the real value to collect after.