Correcting a paid invoice

I can help you with your transactions, @Boxwood.

You can delete that bill payment check that you’ve created. Then, recreate it to set the credit. 

Here's how:

1. Go to your Vendors menu and then Vendor Center. 
2. On the page that appears, proceed to the Transactions tab and click Bill Payments.
3. Click the transaction and then click the Delete icon at the top. 

To record a vendor’s credit:

1. From the Vendors menu, select Enter Bills.
2. Click the Credit radio button and provide the Vendor name.
3. Tap the Items Tab and enter the items with the same amounts as the refund check.
4. Click Save & Close.

Once done, you can now link the deposit to the vendor's credit you've setup:

1. Go back to the Vendors menu and click Pay Bills.
2. Check the Deposit that matches the Vendor check amount.
3. Select Set Credits.
4. Apply the Bill Credit you created earlier then click Done.
5.  Click Pay Selected Bills.

For additional reference, you can check this article: Record a vendor refund in QuickBooks Desktop.

Please know that I'm just a post away if you have any other questions about the vendor's credit. Have a good one.