Hello there, dale9.
Thanks for checking in with us. I'm here to help and guide through on how to handle your concern with offsetting credits from vendor invoices.
You can record this entry into QuickBooks using barter transactions. This process is used to record exchanged transactions between you and your vendor.
Here's how to create a Barter Account:
To create an invoice:
To receive a payment:
Click the Plus icon (+) then select Receive Payment.
Select Save and Close.
Now you ready to enter and pay the bill for the barter transaction. You can check out this visual guide for the steps on how to do it: Entering bills in QuickBooks Online (Tutorial).
Also, to know more about recording barter transactions in QuickBooks Online, here's a great article that you can refer to: How to record a barter transaction.
There you have it. All the information above should guide you through the whole process. I'm just a post away if you have other questions about this. I'd be happy to help you some more.