said by JoelC707 :

Must have been lucky the manager handled it like that or it was the "corporate" training that helped. I went to a recently opened "mom and pop" restaurant here in Atlanta a few years ago and like you I paid the meal on my card and the tip in cash. Also like you I found the transaction on the card was higher than what it should be, about 18% worth or the amount of a fairly average tip. I discovered it that night when I checked my balance online (paid with a debit card actually) and immediately went back up there.

Now to clarify the waiter knew about the cash tip before the card was swiped so it wasn't an honest mistake. Do you know what the manager told me? He told me that banks see it comes from a restaurant and automatically add in 18% for the tip amount. I promptly spit out the word "bullshit". The manager basically said that by the time it actually posts (I took up a print out of the bank statement and the slip) it would be the correct amount. He wasn't very helpful at all but the next time I went there I noticed the waiter was no longer there. The restaurant has changed hands a few times since then so who knows if the manager was really the one behind it to help pad his bottom line.

said by JoelC707 :

Must have been lucky the manager handled it like that or it was the "corporate" training that helped. I went to a recently opened "mom and pop" restaurant here in Atlanta a few years ago and like you I paid the meal on my card and the tip in cash. Also like you I found the transaction on the card was higher than what it should be, about 18% worth or the amount of a fairly average tip. I discovered it that night when I checked my balance online (paid with a debit card actually) and immediately went back up there.

Now to clarify the waiter knew about the cash tip before the card was swiped so it wasn't an honest mistake. Do you know what the manager told me? He told me that banks see it comes from a restaurant and automatically add in 18% for the tip amount. I promptly spit out the word "bullshit". The manager basically said that by the time it actually posts (I took up a print out of the bank statement and the slip) it would be the correct amount. He wasn't very helpful at all but the next time I went there I noticed the waiter was no longer there. The restaurant has changed hands a few times since then so who knows if the manager was really the one behind it to help pad his bottom line.

said by ODYSSEY :

Older credit card software actually will add a fixed percentage (estimated tip) to the total for authorization (hold). If an actual tip is not inputted, then in three business days after the terminal is settled the original total is charged.

This method protects the merchant, because otherwise if the amount of the tip is not available, then the merchant normally eats the cost.

When a DEBIT card is processed most banks immediately remove the amount authorized, then credit any difference back.