How can I stop these annoying requests to add c/c payment......EVERYtime we do an invoice?

That isn't the experience we want you to feel when doing a task, landerson1.

Let me provide you details on the prompt you're seeing when creating an invoice. They are in-product that are designed to suggest users enabling their Payment features in Quickbooks. You might consider using this feature so you'll easily get paid using a credit card. 

For now, the only way to get rid of this prompt is to click the X or No Thanks option. Since there's no direct way to turn this off, I'll make sure to send this feedback to our developers so they might consider adding this feature to their future product updates.

Here are articles you can check about accepting and processing credit card for your reference:

• Credit card processing.
• Get paid and stay organized with QuickBooks Online.

I'll be right here to help you out if you have any other related concerns. Have a great weekend!