What if a bar charges my card twice?
What if a bar charges my card twice? Simply call the restaurant and explain the error. They shoild be able to corrrct the error (usually by canceling the duplicate charge) with your credit card provider.
What happens if you accidentally write the wrong tip?
It depends on what you mean by “tip wrong.” If you mean you wrote down a number as the tip and then added it up wrong for the total, it could go either way. Some servers will never notice the math error and just enter the total you wrote as the final sale amount.