Let me shed some light with regard to your concern, @jen-glassco-gmai.
 

You can go ahead with recording the vendor credit and enter a positive amount. Doing so will affect the accounts payable thus creating credit in vendor balance. Here's how:

1. Click the + New button, then select Vendor credit.
2. Choose the vendor from the drop-down.
3. Select the Category details or Item details depending on how you record your purchase.
4. Hit Save and close.

Here's an article you can read more about creating and managing credits from your vendors in QuickBooks.

To give you more tips about managing vendor credits and recording cash backs in QuickBooks Online, please check out these links:

• How can I record a cash back to my credit card account?
• Learn how to record a refund from a vendor in QuickBooks Online

I hope this helps. Reach out if there's anything I can assist you with. Have a good day.