Roland Perry writes:

In message , at 14:09:37 on Sun, 26 Feb
2012, Stephen Sprunk remarked:
In a UK restaurant you have to add the tip to the bill before contacting
the card company. That's not so very different from my experience in the
USA where they give you the bill, with an empty field for the tip, which
you hand to the waiter *filled in* (along with your card).

The only* way I've ever seen it in the US is this:

1. The waiter presents an itemized bill _without_ a tip line.
2. You either give him cash (including tip) or a card.
3. The waiter swipes the card in the register, which authorizes the card
for the bill plus an estimated tip.
4. The waiter returns with the card and two slips showing the subtotal,
empty tip line, and empty total line.
5. You fill in the tip and total on the "merchant copy" slip, sign the
slip and hand it back to the waiter. You can leave now. (You should
also fill the tip and total on the "customer copy" slip, for your own
records.)
6. The waiter enters the tip into the register, which updates the credit
card transaction with the correct total for when it's posted later.

That just shows things are indeed different in different countries.
In the UK I have never been asked for pre-authorisation in a resturant, would
walk out if I was. Some pubs you pay when you order, but that is
payment, you pay again with a different transaction if you order
anything else.

At Pizza Hut you pay when you leave, what would they do if you are paying by cash?

Hotels tend to do this, but never sure why as they have your card
details when you book, so that they can charge you if you don't turn up.