Why do restaurants seem to be able to take what they want (hopefully what you wrote as tip?) from your credit card in USA?
Thanks for the A2A.
Restaurants cannot "take what you want" from your credit card - whether you are in the United States or not is irrelevant.
You are probably referring to the fact that restaurants will run your credit card and then add an additional amount onto it for the tip after they have already run the card. First, you need to understand that when you run your card you are only reserving that amount from your account. It doesn't actually get charged. For most retail transactions, the amount reserved will be the same as the amount charged when the batch is settled (usually at the end of the day or sometimes the next day).
But there are exceptions. When you reserve a rental car, for instance, they put an amount on your credit card that is the estimated amount for the rental. But when you return the car, they may charge a different amount based on the number of miles you drove, or the amount of gas they had to put in the vehicle. This final amount is called an adjustment and it is the same process servers use to adjust the total of your bill to include the tip.
To summarize, the amount charged is not finalized until the batch (which includes all charges for that day) is settled. It is only then your card is actually charged. This allows for corrections as well as adding things like the tip. Most credit card companies today will immediately show the amount including the adjustment in your account as soon as it is entered.
Restaurants are obligated to only charge the amount you have approved. Sometimes even that doesn't work out. We recently had a customer who challenged a charge of $60, insisting he only intended to pay $40. We emailed him the receipt and showed where he wrote $60 and then signed the receipt. He apologized and said he entered the wrong amount. So we refunded the difference.