How can I flag a customer account as a bad payer to avoid further goods being issued ?

Let's use the Notes field so you can flag a customer's profile as a bad payer in QuickBooks Online (QBO), @gabbydewet. This way, you'll be reminded not to issue further products or services to them. The field lets you enter information with a maximum of 4,000 characters. I'll guide you how.  

1. Go to Sales from the left menu. 
2. Select Customers.
3. Locate and choose the appropriate customer from the list. 
4. Click Edit to open the Customer information window. 
5. Go to the Notes tab.
6. Enter the information in the Notes field like this, "This customer is a bad payer. I want to avoid issuing further goods to them." 
7. Choose Save.

The screenshot below shows you the last three steps. For the detailed instructions, check out this article: Use Notes In QBO. 

I recommend running the Customer Contact List report from the Reports menu. Then, customise it by adding the Note column in the Customise report window. Doing so will help you include the notes on the report to identify the customer. I've attached a screenshot below on how it looks like in QBO. 

I'm here anytime you have other concerns. Keep safe always, @gabbydewet.

@gabbydewet 

If you are having an inventory management app, you may set no credit limit to the customer to avoid anyone in your company process any sales order.