In message , at 18:32:17 on Sun, 26 Feb
2012, Adam H. Kerman remarked:
UK credit card statements (including Amex) don't usually have
transaction numbers.

Ok. I bet the transactions are numbered, though.

Internally I expect they are, but the numbers are not revealed to the
cardholder.

What I was disputing was your retailer "two pass model", with the card
itself being authorised up to some "reserved" amount, ahead of the
actual amount being claimed milliseconds later by the retailer.

The card isn't swiped twice.

In a C&P terminal it's not swiped at all. "Inserted" would be a better
verb.

The merchants receives data in two steps.

You'll have to tell us what's in these two [rather than one] steps
(genuine question).

I don't know why they'd do that, rather than ask for authorisation of
the actual amount first, because in the UK the amount has to be known
before you enter your PIN into the C&P device, as entering your PIN is
an agreement to pay that precise amount.

Uh, always? What do you do at a fuel station which requires a credit
card before dispensing fuel,

That's an exception, because of the way self-service pumps work (they
check the card first, then make the charge later).

or at a restaurant, when the tip amount to be charged is not known
until later,

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).

or at a hotel that requires a credit card to create a reservation and
the same one or another one to check in?

We've covered multi-day charges like this.

The two-pass scheme is used in other circumstances, such as checking
into a hotel, when they often "reserve" an estimate of the final bill,
ahead of the day you eventually check out.

Ah. So the amount isn't always known. Do you provide the PIN
at that point, or not?

Yes. They appear to make a small charge (maybe ten dollars) which they
credit later, once the real amount of the "extras" is known the day you
check out.

Hotels, rental car companies, may bill you for charges after you are
presented with the final bill.

And special arrangements exist for those circumstances. Being by
definition "customer not present", I expect they are more at the
merchant's risk than charges they levy while you are still on the
premises.
--
Roland Perry