Can a supplier also be a customer. I have to make an invoice for a supplier, but when I click on customer in 'invoices' it says that that the name is all ready in use?

I've got you covered, @userilanamaree1.

QuickBooks treat suppliers and customers as separate. The only way to add a customer, who is also a supplier, is by adding a special character or any distinction to identify which one is the supplier or customer.

Here's how:

1. Navigate to the Sales menu and select Customers.
2. Click New customer.
3. Enter your customer's name. You may add "(c)" at the end, e.g John Smith (c).
   
4. Enter the necessary customer information. 
5. Click Save.

These instructions are also available from our guide on adding and managing customer in QuickBooks Online.

You can also check the informative write-up about recording a barter transaction. It has detailed steps on handling exchanged goods and services between you and your supplier.

Let me know if there's anything else I can do for you. I've got your back and am always willing to help. Wishing you all the best!