Was at a bar last weekend and when I closed tab I was handed a reciept w/ total amount and tip line. Luckily I added tip and signed the customer copy before I realized it seemed high. When I asked for itemized copy, I could tell something was up as it took forever and a day. I saw where there were a few drinks that weren't mine, and 18% gratuity. I was pretty PO'd that I wasn't given that first since I added a tip -not additional tip like they normally say- and that the tip was hidden in the bill. I asked for my copy back so I could remove all tips and dispute the other drinks, I was ignored as the bar was closing...I then noticed that I had not signed their copy at all.
I have been unable to contact management and suspect when I do they will probably act concerned, but be well aware of how this works. I have contacted AMEX and disputed the all the charges except for my drinks not including any tip. Without a signed copy, I assume I will get it back...but will AMEX just credit my account, or actually take the money, and more importantly the tip from the sly ... bartender, back from the bar?

I wouldn't have left the bar, and would've asked to speak to management then.

I started a similar thread a year or two ago. In my case it was being overcharged after having a lot to drink.

Looking back I should have, but I was ready to go and was pretty confident AMEX would handle it in a calmer manner than I would have at that point.

Really, is this this first time it's happened to you?

This happens all of the time. Servers/bartenders will add a few dollars on bill. If you see an instance of this, call your credit card company and they will take care of it for you. I have had this happen several times.

I always tip in cash. Don't let the bar determine what you tried to write after drinking....

Haha - I actually try not to carry cash when I drink because I will spend/lose it, etc!

This is exactly why I make a habit of keeping receipt copies from bars and restaurants and, once a month, match them to my online statement. Believe it or not I've caught a handful of unauthorized extra-tip-adders this way and said something.

I've had this happen a few times in the past. If management is not there or unresponsive, the course of action I take now is to place a big "NOT SIGNED" in the signature column. Then I promptly dispute the entire bill with AMEX. Usually the full amount of the charge will be deducted from your monthly statement.