How to record the advance payment on accounts payable beginning balance?

I can help you with recording an advance payment for your vendor, @accounting-emint.

You can record an advance payment for the supplier using the Expense feature. You'll just set the payment as an Accounts Payable. 

Follow the steps below:

1. Go to the + New button and select Expense.
2. Choose the Payee name and Payment account.
3. Go to the Category details section.
4. Under the Category column, select the Accounts Payable (A/P).
5. Provide the description and the amount.
6. Click Save and close.

Refer to the following article for more information about adding, editing, reviewing, and deleting an expense: Enter and manage expenses in QuickBooks Online.

From here, you can run the Income by Customer Summary report to review income and expenses for each of your customers. Here's a detailed guidance about generating and customizing your report: Run reports in QuickBooks Online.

Let me know if you need further help or guidance about adding your advance payment. I'm always here to assist. Have a great rest of the day!