QuickBooks will automatically calculate the total sum of all transactions shown on the Transaction List of your vendors, accounting661.
To ensure it is zeroed out or can be applied to a future bill, ensure the expense is categorized under Accounts Payable (A/P).

To link the expense to your bill, follow these steps:
- Navigate to + New.
- Click Pay bills.
- Choose a vendor, then find the bill.
- Click the dropdown arrow under Action and select Mark as paid.
- Check the box beside the Bill and Expense.
- Hit Save and Close.

Please note that it's normal behavior for QuickBooks to add all the transactions and display them in the total column. To verify that the credit was applied, you can check the open balance instead.
For future reference, you can scan this material to generate a comprehensive report of all vendor payments made throughout the year: Run a report with vendor totals in QuickBooks Online.
If you need help managing your transactions, consider our QuickBooks Live Expert Assisted service. Our team of experts is ready to assist you in optimizing your financial operations to suit your business needs.
Please don't hesitate to get in touch if you have any further questions about managing your vendor's open credit or other concerns related to QuickBooks Online. We're always here and ready to assist you.