[rivo]

Some larger retail stores in Germany ask you for your postcode during checkout, presumably to learn a bit about their customer base. I don't mind telling them mine, there are about 16K people with the same postcode. But I'm pretty sure I would not tell them if I was one of the two forest rangers in Reinhardswald. (And yes, I do pay cash whenever I can.)

[ryukoposting]

Interesting, is the German postcode not used for transaction validation? I know the American payment processors definitely use ZIP codes for validation - see anecdote 1.

That said, there are definitely situations where the payment processors don't require the ZIP code - see anecdote 2.

Anecdote 1: When I worked in food service as a kid, I used card terminals that connected directly to a phone line. I remember a couple of times when I entered the ZIP code incorrectly - the card terminal would print out a receipt with an angry message saying the transaction got rejected. So, I know they were using the ZIP code to validate the transaction.

Anecdote 2: With those same card terminals, you could skip the ZIP code and it would run the transaction as usual. But, my manager always told me not to do that. Maybe I never asked him why, or maybe I forgot his answer. Regardless, I don't remember why we he required us to enter the ZIP code, even when it didn't seem to be necessary.

[quesera]

ZIP codes are used as a weak "something you know" factor in payment card processing.

The card is (for card-present transactions) "something you have". And the ZIP complements that. ZIP code is optional, but the merchant gets a data integrity score back from the network ("AVS/address verification service response", from no match to full match), and can accept/decline the txn at their discretion.

Because it's optional and at merchant discretion, all it really does is give the merchant some additional ammunition when disputing a chargeback. And of course to build a demographic database.

[lilyball]

The answer to anecdote 2 is probably that if the seller chooses to skip validation measures on the transaction, then they become liable in the event the transaction is deemed fraudulent.

[kwhitefoot]

> is the German postcode not used for transaction validation?

No. The only time I have ever been asked for a post code was when a petrol pump in the US demanded my zip code. I have no idea what it meant, I just put some random zip code for the general area I was in and it was accepted. I've never been asked for my post code in Europe; I can't speak for the whole of Europe though, just UK, Spain, Ireland, Portugal, France, Belgium, Netherlands, Italy, Germany, Poland, Denmark, Sweden, Norway.