Good day, @Arzini.

You can create a penalty item to charge the customers for outstanding invoices.  Here’s how:

1. From the Lists menu, choose Item List.
2. Click the Item drop-down arrow and select New.
3. Pick Other Charge under Type.
4. Name the item.
5. Provide an Amount or % and Account.
6. Hit OK to save the item.

Once done, create an invoice for the item. You may have to manually calculate the penalty amount depending on the guidelines provided for charging late payment fees. Follow these steps:

1. From the Customers menu, select Create Invoice.
2. Select the penalty item.
3. Enter the penalty amount and the description.
4. Hit Save & Close.

Check out these article for the details: 

• Add, edit, and delete items.
• Create an invoice in QuickBooks Desktop.

Leave a comment if you need anything else. I’m more than happy to help. Have a fantastic day!