UK Switch

[Philip Rowlands]

On Wed, 5 Jun 2002, Roland Postle wrote:

>They usually ask for the valid-from date and/or the issue number. Not all
>Switch cards have the issue number, but where they do it seems to be very
>important.

I think this is because the card number is derived from your account
details, e.g. <standard prefix>+<sort code>+<account number>+<check
digit>. That's certainly how it appears for my Natwest card.

Therefore, when fraud or card loss occurs, they can't create a new card
number, only a new issue number. Without it, the transaction is
probably refused. The issue numbers are, in my experience, both highly
predictable and sequential.


Cheers,

Phil