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In ISO8583 there is STAN field 11 which is a continuously growing number that identifies transaction. How can I generate one in case of PSP? Should it be assigned per tid or mid and growing independently for each of them or globally per PSP? When should this field be reset to 000001 - after reaching limit 999999 or, for example, daily, regardless current value?

Pika Supports Ukraine
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krzykol
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    This is not well researched / high level question. Generally covered in each ISO-8583 specification. It is also effectively a duplicate and not uniquely different enough from: https://stackoverflow.com/questions/56385566/could-the-stan-number-be-repeteable-and-random/56399548#56399548 – CRSouser Jun 04 '19 at 14:13
  • Agree with the above. Please also note that STAN does not identify transaction and it may be very problematic if you choose to implement it this way. – Michal Gluchowski Jun 05 '19 at 06:59

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I don't know of any requirements, though, that say it must be ever increasing. I believe it should be non-zero.

The STAN requirements can vary across card brands. For example, Mastercard requires the value sent to be unique within a single merchant location or terminal per 24 hour period.

Also, you can run into variations between card brands on message types other than 0100/0200. For example, some card networks requires the STAN on a reversal (0400) to match that of the original transaction. Others want a new unique value in the reversal.

That said, quite often the STAN used is simply the terminal transaction sequence number sent by the POS. That generally solves the problem of uniqueness for authorizations.

user12265894
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Typically globally by PSP, but your acquirer may need per TID, you have to check with them.

apr
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