I'd be glad to guide you on how to pay bills using supplier credits.
You have two steps to pay the bills in your QuickBooks Online account. First, you'll need to enter/record the supplier credits. Once done, you can now pay the bill using the credits. Here's how:
To enter the supplier credits
Click the +New button.
Choose Supplier Credit.
Select the supplier name in the Supplier field.
Enter the Date, Amount, and Account (the account used here is typically the original expense account on the original bill).
Hit Save andclose.
To pay bills using the credits
Click the +New button.
Choose Expense or Cheque.
Select the supplier name in the Choose a payee drop-down.
Leave the Ref/Cheque no, Date, Amount, and Memo fields blank.
Select Add for the outstanding bill and the supplier credit.
Hit Save andclose.
I'm also adding these handy articles for you to learn more on how to record and handle supplier credits and refunds.