That isn’t unusual, but I believe it is against their biller agreement with their financial institution. From what I’ve seen, the biller agreements all appear to be the same, and I’ve had billers ‘reprimanded’ (apparently) and change their wording and behaviour by making a complaint.
They key point is “Settlement Date”
For example: BPAY Biller - Operations Manual, CommBank
On Page 3:
1.Your general obligations
You must:
[…]
(treat Payments as being made on the
Settlement Date) for the purposes of obligations
owed to you by your Payers, treat Payments to
you as being made on the Settlement Date;
Page 9:
9 Meaning of words
[…]
Banking Business Day means any day on which banks
in Melbourne or Sydney are able to effect settlement
through the Reserve Bank of Australia.
Biller means you as a participating biller, and any other
person who has entered into an agreement with a Biller
Institution on substantially similar terms to those in your
Biller Agreement.
Page 11:
Payer means a Payer of a Biller who uses BPAY
Payments to make a Payment to a Biller.
Payer Direction means a direction from a Payer to their
Payer Institution to effect a Payment to you as a biller
through BPAY Payments, by debiting (for example, a
payment) or crediting (for example, an Error Correction)
an account or facility held by the Payer with that Payer
Institution.
Payer Institution means a financial institution
participating in the BPAY Scheme with whom a Payer
has an account facility from which payments can be
made and who receives a Payer Direction from that
Payer.
Payment means a payment made, or to be made, by
or on behalf of a Payer to you as a biller through BPAY
Payments.
Payment Cut-off Time means, with respect to a Payer
and its Payer Institution, the time on a Banking Business
Day set from time to time by that Payer Institution as the
time by which that Payer Institution must receive a Payer
Direction for it to be included in a Payment Instruction
processed by it or sent to the CIP on that day.
[…]
Settlement Date means the day a Payer gives a Payer
Direction to its Payer Institution. However, if the Payer
gives the Payer Direction after its applicable Payment
Cut Off Time on a Banking Business Day, or on a non
Banking Business Day, the Settlement Date is the next
Banking Business Day.
So if you pay the bill on the due date, and the due date is a banking day, and you direct the payment before the cut-off time that day, you have paid on time - regardless of when they get the cash. There does not appear to be a clause in any of the agreements I’ve perused that allows them to modify the concept of “settlement date” … I’d be very keen to hear if there are legitimate exceptions to this agreed by Bpay per agreement, or more specifically non-standard agreement. I do know Bpay don’t always press the issue - some entities appear to be untouchable - think feds …
Back to the subject - I pay a number of bills through Bpay with credit card - with no issues. In cases where the biller does not accept credit card I get an message on CommBank that the biller does not accept credit card and I need to change account type for the payment before it can be submitted.
