[RichieAHB]

It feels like that might be a fair point in other context but as one of your sibling posts says: this is just double entry book keeping.

Print out the transactions with their timestamps and it feels this should have been very clearly a computer error given the duplicates etc.

[cge]

I recall seeing in released emails about the Callendar Square bug that it's debatable as to whether what the system was doing was properly double entry. In that case, my interpretation of the emails was that there were transactions that were nominally recorded as multiple double-entry transactions, but involved, eg, a transfer from account A to a hidden outstanding account X, and a transfer from account from X to account B. Then the account X wasn't actually tracked anywhere or even expected to balance on any individual system: it appears that when multiple counters at the location were involved, the transactions weren't necessarily synchronized between them. In that case, if you have three £1k transfers from A to X (two of which are duplicates), and one £1k transfer from X to B, then it will look like £2k disappeared unless you check the balance of X.

To me, that sounds like an accounting system made by people who fundamentally didn't understand the point of double-entry accounting, because a double-entry accounting system that uses hidden or untracked accounts entirely removes that point and is just equivalent to a single-entry accounting system. Presumably, if all those transactions were properly stored and then combined, a full double-entry ledger could be reconstructed, but it appears the system itself couldn't do that in at least some cases.

Of course, there also seems to be the suggestion that part of the Post Office's argument to subpostmasters was that even if the problems were obvious, like clear duplicate transactions, they were still liable per the contract.