But Friday transaction / settlement arrives Tuesday and sometimes Wednesday - AMEX nowhere near as consistent
This is not AmEx's fault. It makes perfect sense if you think about it.
APCA process the last interbank settlement for a working week on Friday night, with this process completed on early Saturday morning, so funds would arrive in their destination accounts Saturday morning. The next one will be Monday night (there is no interbank settlement on weekends),
The very latest / last cut off time I know of for fund transfer, is 6PM Sydney time (with the big 4 banks + HSBC).
When your EFTPOS terminal settles, it would probably be around 6PM, or well after 6PM. This means AmEx would have well past the cut off time on Friday night, the very last for the week, to send you the money.
APCA does not do interbank settlements on weekends, so you don't see your money over the weekend.
The first interbank settlement for the week is processed Monday night, completed Tuesday morning.
So AmEx receives your takings from Friday on Friday night, missed the last interbank settlement for the week, the money sits in the queue until APCA send you your money on Monday night, and your bank receive and process your money on Tuesday morning.
The same process applies if someone sends you money using Internet banking. If they do the transfer after Friday cut off of their respective bank (big 4 are 6PM Sydney, HSBC is 6PM Sydney, Suncorp is 4PM Brisbane, other banks & credit unions can be as early as 1PM), you won't see the money until early Tuesday morning.
banks with Visa / Mastercard IMHO - who ALWAYS settle following day - Friday's funds arrive Saturday / Saturday's funds arrive Sunday.
This only applies if your merchant facility and the bank account for receiving fund is the same bank.
So, if your EFTPOS is from ANZ, and the money is to be sent to an ANZ account, then yes, Friday night settlement, and ANZ can put the money into your ANZ account the same night.
This is not possible if your merchant facility is from a different bank to your bank account.
If your EFTPOS is from ANZ, and the settlement is say 7PM, ANZ may have missed their own cut off time for sending money to another bank. If this is the case, ANZ will finalise your EFTPOS taking on Friday night, and your money will sit in ANZ, until APCA process your money on Monday night, and arrives in your bank account with another bank (say Westpac) on Tuesday morning.