How do you apply a vendor credit to an open bill

Thanks for reaching out to us, 2sincorp.

I'll be delighted to guide you in applying a vendor credit toward any open or future bill. In case you haven't created the vendor credit yet, feel free to follow the steps below: 

1. Click the + New icon.
2. Select Vendor credit.
3. In the Vendor drop-down menu, select your vendor.
4. Enter the necessary information.
5. Choose the appropriate category details or item details.
6. Select Save and close.

Once done, we can now apply it to an open bill:  

1. Click the + New icon.
2. Select Pay bills.
3. Select a bill for your vendor from the list.
4. You'll see the available credit with this vendor in the Credit Applied field.
5. Enter the necessary information.
6. Click Save and close when you're done.

I've included an article that will help you track all money you've paid to a vendor for a particular date range: Run a report with vendor totals.

If I can be of any additional assistance, please don't hesitate to visit the Community again. Have a pleasant weekend ahead.