Why your order system and your payment provider disagree

The useful part

Or, the one that ruins the afternoon, a refund larger than anything that was ever collected. Operations says the payment system is wrong, engineering says the order system is wrong, somebody exports both into a spreadsheet, and the spreadsheet becomes the thing everyone argues about instead of the systems. A decision gets made in the end because the week ran out, not because anyone worked out what happened.

How it works

• I've watched this in banking, in healthcare, in gaming and in public administration.
• The basket changed and nobody wrote it down A customer starts a checkout at €120, adds something, pays €150.
• Pull the two exports on different days and they're €30 apart, and neither of them is lying.
• This is the common one, and there's nothing broken: the records describe two versions of the same purchase, and nothing in the export tells you which version you're holding.
• You'll spot it because the same order identifier carries two totals, or because a total moved between one export and the next.

What to take from it

There's nothing to do to the money вЂ" fix the export so each version of a basket carries its own identifier, and the disagreement stops existing. One payment, taken in two goes A €150 order captured as €100 and then €50.

Details worth keeping

Twice a month somebody in operations finds a number that doesn't match. An order recorded at €120.00 against a capture of €119.40. Every team was sure their situation was unusual.