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> Assuming the last digit is a checksum and the first six are taken by the routing information, that leaves them 9 digits or a billion possible numbers per credit card issuer. Japan has a population of about 125 million. Are Japanese people cycling their numbers so frequently? Or are they big on ephemeral card numbers?

Credit cards - and payment methods generally - are in their Cambrian explosion phase right now in Japan, particularly given the pandemic. Every company, big or small, is pushing their own. I recently had to open a new credit card because the gym I wanted to join only accepts payment via their partnered credit cards. It came with a linked electronic money card (as well as having native integration for a different electronic money format) that has what looks like its own 16 digit credit card number, presumably for internal payment infrastructure reasons, and an offer to apply for a separate linked credit card for shopping in China, three other kinds of linked electronic money cards (one for a supermarket chain, one for a local transport network)...

Every shopping mall is pushing their card. My phone provider offered two olympic tie-in cards and a regular version (that would actually save me money if I could face going through the application). A theatre troupe I follow has a deep partnership with a card issuer and has their own branded cards. Bands have their own cards. Virtually any outfit with a loyalty/membership card is trying to turn it into a credit card. And so people can easily have multiple cards that they never use, because their loyalty card became a credit card but they're still only using it as a loyalty card.



Most of these "branded" cards will have an underlying issuing bank/acquirer, not their own identification on the card.

The way that the 16 digits are allocated is defined as per https://en.wikipedia.org/wiki/Payment_card_number#Structure

So of the 16 digits for the majority of cards:

Digit 1-6(8): Scheme and issuer identification Digits 7-15: Account identification Digit 16: Check digit (Luhn algorithm)

So most issuers have 10 digits to "play with" to identify the account.

So Japan is either running out of issuer identifiers, which sounds excessive, or they have been allocating them badly.


Sure, but if I have 8 different cards issued by SMBC then that's still 8 cards.


Seconding this. I have multiple cards by SMCC, some basically given to me.

There's also a lot of "virtual credit card" offerings right now to pair with peer-to-peer payment apps. I imagine that those need to get cycled through frequently.

8 is not an exageration.


Ah, here's the real explanation! Interesting.

I wonder how big the incentive is, and if anything changed to enable this. As for the incentive, I'd guess they get transaction fees cut from some ~2.75% to 0.5%ish with their own card, and then some kind of additional cash (maybe $50-$300?) from the issuing bank for gaining a customer?


I don't know why it's exploding, but it also appears poised to explode here in the US too. I recently got a recruiter in my inbox for a startup "Guild Credit" that makes loyalty CC cards easy to issue for small businesses. Not sure what has changed recently.




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