re: Qantas Cash Card
I had no pre-authorisation on the card.
You may not know if you did.
Every transaction settled through MasterCard/Visa potentially starts with an authorization (whilst my knowledge is a bit dated, I don't think anything material has changed). Just about all electronic (swipe etc) transactions are now authorised.
The batch settlement processing then matches up the actual transaction, and removes the auth. Sometimes (especially when delays occur, forex conversion is involved, and exchange rates are volatile), the actual transaction amount ends up sufficiently different from the original authorization amount, that they do not match, and the authorization remains until it expires (authorizations eventually expire to allow for this, and for transactions never being processed).
Another source of extra authorizations is the lag involved when terminals (ATM and Eftpos) are processing. If they don't get a response on time, they time out, reverse the attempted transaction, then retry. Timeouts become more common when you are at the end of a long chain (think in Europe, via card scheme, eventually ending up at a minor bank in Aus). Some terminals automatically retry. It is possible for attempted tranaactions to authorize, but the response doesn't arrive until after timeout. If the reversal doesn't work, or gets lost, then "extra" authorizations can end up left against the card until they expire.
Depending on the account type, they may or may not be visible, but they will affect the available funds for other transactions. If you don't check until after they have expired, you can't tell whether or not they were present, other than by inference as to how other transactions behaved.
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