Hi rfocroft,
Thanks for reaching out to us here. QuickBooks is a versatile program that's designed to help you with your accounting. I'll be glad to assist you going forward.
The ability to turn off payments is available when creating/sending an invoice. For example, when creating an invoice make sure to uncheck the Online Payment options checkbox at the top of the page. Doing this won't send an online payment prompt to the customer. You're welcome to ask other questions in the comments below.
I'll be one message away!