Let me help you sort this out, Ash Gascoigne.
The supplier's credit will show as a transaction when you open the Transaction List report. It's normal when you apply it to a bill.
However, if you're referring to a zero transaction, we'll check it out. You'll have to click the amount so you can see the details. If it was mistakenly created, you can delete it by clicking More, then selecting Delete.
I'll include this article to help you know more about credits and refunds: How do I handle supplier credits and refunds?.
Don't hesitate to let us know if you need our help. We're available 24/7 to assist you. Take care!