Hi there, Ramy2. 

I can share some information regarding the negative entry on your sales in QuickBooks Online (QBO).

When customers make a payment to an invoice, an overpayment may happen of the time. This is the reason why you're seeing a negative balance upon reviewing the list of their transactions.

You'll have to check if these are duplicates or not. Then, check if there should be an invoice to apply it to. Create one if needed.

To apply the credit to the invoice, let's follow these steps.

1. Go to the +New button.
2. Under Customers, choose Receive Payment.
3. Verify that the credit and invoice are both selected and that the amounts are equal.
4. Once done, hit Save and close.

Apply the credit to a new invoice:

1. Go to + New in the left panel and choose Invoice.
2. Create the invoice.
3. Click +New and select Receive payment.
4. Select the credit and then Save and Close.

For the complete steps, we can refer to this article: Create and apply credit memos or delayed credits in QuickBooks Online.

If everything is good on your end and you'd want to personalize invoices and other sales forms, see this: Customize invoices, estimates, and sales receipts in QuickBooks Online.

You can always get back to us if you have other concerns managing invoices, credits, or QuickBooks as a whole. Just hit the Reply button so we can respond as soon as we can. Have a great day!