Blocking occurs when a merchant, typically a hotel, car-rental agency, gas station, or other product or service provider, puts a hold on your credit or debit card for a certain amount of money in advance of a final purchase. Blocking is typically done when a charge is authorized before the actual billing amount is known. Blocking is often done for an amount higher than the actual purchase. For example, it is not unusual for gas stations to block $50 or $60 on a credit card before someone pumps gas into their car. Blocking can cause problems (e.g., over-the-limit fees) with credit cards that have balances close to the credit limit. It can also cause problems with debit cards that are linked to checking accounts with low balances where a block can lead to bounced checks.
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