We are facing some issue about Refund to customer, we have to apply refund receipt but refund receiot not aplly apply in sale invoices or Sale Invoices balance.

In QuickBooks Online, a refund receipt does not specifically apply to the sales invoice, Kasim-ali.

A refund receipt is used to record returned items or services. Alternatively, you can issue a credit note to apply the refund to the sales invoice. 

To learn more about creating a credit note, follow the steps outlined below: 

1. Select + New.
2. Select Credit note.
3. From the Customer dropdown, select the customer's name.
4. Enter the credit note details, such as the date and the amount.
5. You can create a custom credit service item so you can quickly add it to credit memos as a single line item.
6. When you're done, select Save and close.

Once a credit note is created, it can be applied to an invoice to adjust the balance accordingly.

Here's how: 

1. Navigate to the Receive Payment section.
2. Select the customer, and then check both the invoice and the credit note.
3. Ensure the amount applied matches the credit memo's value and save the transaction.
4. This will mark the invoice as paid and close the credit memo. 

Refer to this article for detailed instructions on creating and applying credit notes: Create and apply credit notes or delayed credits in QuickBooks Online. 

Let us know if you need more information about managing your sales invoices in QBO. We're always here to help.