I need to out the opening balance of the customer which i have received amount against the items which already sold

Let's receive the payment on an invoice to zero out your customer's opening balance, shakirarain. It's my pleasure to guide you through the process quickly and easily.

If you've created an invoice for the sold items, we can locate it and record payment directly to clear the amount. I'll show you how.

1. On the left panel, select Sales.
2. Click the Invoices tab, then filter the Status and Date.
3. Tap the Receive payment once you find the transaction.
4. Enter the payment amount.
5. Hit the Save and close button.

Here's an article for complete instructions: Record invoice payments in QuickBooks Online.

On the other hand, please know you'll need to choose the invoice from outstanding transactions and pick the credit memo to be applied if it's an overpayment. Check this reference for your guide: Handle a customer credit or overpayment in QuickBooks Online.

Additionally, this link will help you associate the sales and bank register entries: Link a bank deposit to an invoice in QuickBooks Online.

For future reference, save these materials about personalizing the forms and reviewing accounts to ensure the accuracy of your books:

• Customise invoices, estimates, and sales receipts
• Reconcile an account

I'm always here to back you up whenever you need help with your receivables. Leave your additional concerns about managing customers below, I'll get back to you as soon as possible.