Fines - Credit card due date varies

These late payment charges might be considered unenforceable penalties, or an unfair contract term. I don't think either interpretation has been tested in court, AFAIK.

On the few occasions I have challenged them, the credit card companies have refunded them.

Yes. Many years ago I missed a Barclaycard payment. The due date, within the month, had advanced by perhaps ten days over the preceding years. Whether that was really the reason I missed it, I really can't remember, but I complained on that pretext (in writing) and they refunded the charges.

I can't think of a good reason why (some of) the CC providers vary the date like this, other than to net a few late payments each month. Maybe someone else can.

Ah, yes. The strange but seemingly immutable law of accountancy gravitation. I've watched with interest as several of my utilities budget plan direct debits have drifted towards the beginning of the month and piled up like driftwood under a groyne whereas regular payments received move in the opposite direction. My SIPP providers raid the bank account for my pension on the first day of the month and pay me on the last day of the month.

Things may work in reverse in the southern hemisphere.

It's probably not personal but a bean counter sliding pay dates on a graph and seeing how the cash flows in sooner if the slider moves left (earlier). Inertia by the punters makes this almost a winner.

One of my cards moved the DD date to *one week* after the dated statement, out of the blue just like that. Result with the sterling Mail service at its best was that the bill arrived after the DD cut in. Cue one call to the card provider to stop the DD since they were in clear violation of the 10-day notify to debit rule. Ever so sorry they were, won't happen again, here let me move the DD date to the end of the month instead of the middle. Obviously the debit date slider is under the full control of anyone in the org!