I have a supplier who we need to pay, but I need to deduct an invoice sent to the same person, (as a Customer). How do I show this correctly in QB

Hello Liza-careandcomp, thanks for posting on the Community page,  so this would be a contra payment you would need to do in QuickBooks if the supplier is also a customer. If you have a look at this help article it has all the steps you need to do to show it in your account. How to enter contra payments into QuickBooks Online.