Bad Debt, Customer Did Not Pay
In the event that you create an invoice and deliver products, but the customer does not pay and you do not expect to be paid, you can handle the invoice by doing the following:
Edit the invoice and change it to a Tax Write-off invoice with the Lost/Stolen/Damaged/Expired Goods option.
Then just enter a 50% discount and no tax like any other Tax Write-off invoice. That still removes the products from inventory, shows your expense and that you were not paid for the products, and you'll have the total for that category of Tax Write-off invoices on your Tax Report.