Hi there, @CaseyHart.

When adding a customer, you have the option to set the primary payment method in their profile. Here's how:

1. Go to the Customers & leads menu and select Customers.
2. Click New customer or locate a customer you want to edit and click on their name.
3. Go to the Payments section.
4. Under Primary payment method, choose Check.
   
5. Click Save.

However, this method only applies when receiving invoice payments. If you need to disable the credit card option for all new invoices, follow these steps:

1. Go the Gear icon in the upper right and choose Account and settings under Your Company.
2. Hover your mouse to the Sales menu on the left panel and click the Pencil icon for Invoice payments.
3. This will show the Payment options section.
4. From there, uncheck the box for Accept Credit Cards.
   

Additionally, you can check out this article in case your customers can't pay for an invoice you sent them: What to do if your customers can't pay their invoices online.

Please keep me posted if you still have questions or concerns about your transactions or any QBO-related tasks. I'll be around for you. Have a great day!