Thank you for joining the thread, @Lcsc450. Let me give you information concerning the vendor credit and pay bills in QuickBooks Online.

For some reason, the credit is automatically applied even it is marked as not available on your end. Just fill-up the remaining fields as usual.

Have this article for you reference in Handling vendor credits and refunds in QuickBooks Online.

I also added this link to learn more about managing your QBO account: Help articles. I’m sure you’ll find it helpful.
 
Don’t hesitate hit reply if you want to know more information in QBO. I’ll be here to assist. Have a good one!