Before proceeding, I'd like to verify if you're referring to the payment terms on your invoices. If so, I'll gladly show you how to edit it in QuickBooks Online.
Go to the Gear icon, then choose All List.
Select Terms.
Click the New button.
Enter a nameand 5 as the number of days, then click on Save.
Once done, you can now add the term on your invoices.
In case you're pertaining to your QuickBooks Online subscription, the invoice payment will depend on its date. We're unable to edit it.
Additionally, I've included these articles that'll help you manage your transactions in QuickBooks Online: