Hi here, bjohnson-expertm.

I'm here to help you post a vendor refund in QuickBooks Online (QBO). In QBO, entering the refund depends on how you record your purchases.

If you enter bills to track expenses, you can create a vendor credit to record the refund. Here's how:

1. Click the + New button at the left pane.
2. Select on Vendor credit.
3. In the Vendor drop-down, choose your vendor.
4. Depending on how you record purchases with this vendor, enter the Category details or Item details. Usually, this is the category, product, or service you’re getting a credit for.
5. Hit on Save and close.

After that, you can now deposit the amount and use the Pay Bills to connect the bank deposit to the vendor credit. 

1. Click + New.
2. Select Pay bills or Pay bill.
3. Select a bill for your vendor from the list. You'll see the available credit with this vendor in the Credit Applied field.
4. Complete the rest of the fields like you normally do.

If you use an expense or write a check, check out this article for instructions: Learn how to record a refund from a vendor in QuickBooks Online.

For your reference, I'm also adding here some articles that you can visit about entering a vendor credit and applying them to your transactions.

• How you enter the credit depends on how you record your purchases
• Learn how vendor credits are applied.

I'll be right here to help you if you have any other questions or concerns. I'll make sure you're all set. Have a lovely day!