And now for this week’s episode of Brian Complains Like a Bitter Old Man (currently in its twenty-fifth season).
Have you ever gotten a bill where the due date says “Due Upon Receipt”? Why do they do this? It’s silly, it’s unhelpful, it doesn’t make any sense.
I get it: they want their money as soon as possible. Everyone wants money as soon as possible. It’s money.
But a due date isn’t for when you want something, it’s for when you need something. That is, it’s the point after which bad things start to happen.
So are they saying that you absolutely must pay the bill as soon as you get it? Of course not (and that would be awfully rude if so).
Can you wait a week to pay it? Almost certainly. Can you wait six months? Almost certainly not. Is there a point between those two extremes where they will start to get upset that you haven’t paid? Yes, and that point is called the due date, and they know when it is, so just tell us when it is.
Argh.
Rant over. Please continue your day.
Brian D. Buckley 
My favorite is the mortgage payment. Due in the first, but there is no consequence if you don’t pay til the 17th. Feels like it may be due on the 17th
I lol’d irl.
If legal terms are the same in the US as the UK, it doesn’t mean due by it means the date from which it becomes due. So, the field is intended to either hold a future date (for example, where the payment is taken automatically from your account, you might get the bill before its due to enable you to make sure the money is in your account).
The UK also has automatic contractual terms that apply if the specific contract doesn’t cover them. So potentially US law has an default term that payment is due within a reasonable period (or within X days) of becoming due.
So the document makes sense if you are familiar with the specific structures of contract law.
Of course, that doesn’t mean you shouldn’t be bitter that the people sending you the bill haven’t made the explanation of how the terms are used clear and obvious.
I couldn’t say how similar US law is to the laws you mentioned. But the ordinary meaning of “due date,” as I understand it – at least in the US – is the date that someone needs something by. So if they’ve got their own special meaning, then (as you suggested) I’d appreciate them telling me what it is.