Hello there, @JAKING.
Right now, we don't have the option to add the due date of an invoice to the statement in QuickBooks Online. As a workaround, you can run the Invoice List report to get their due date details.
Before you go, I want you to know that your voice matters and I'm sending a feedback on your behalf. I'll keep you posted once the feature is added on the online version.
That's it. Let me know how it goes or if you have other concerns. I'm just a post away if you have follow-up questions.