"but unless you have it appear on your invoice (I have it on screen only not to print) the program will not apply it. Glad this is helping a few people"

Once you Assign a customer name their default, that is used, even if you don't show it to yourself, to set the Due Date. However, it doesn't change Existing invoices. Once you assign terms to the name, that is Now available to be used by the program.

On an invoice, you can Show the due date to yourself, and/or to the customer. You see it to control it, to confirm it, to see if you forgot to assign that new customer a default terms, and if you put terms here now, you can have the program "feed this back" to Update that Customer Name with this new option as their Default terms.