This is just the place to get the answers you're looking for, @greencross.

There are times when an invoice becomes non-collectible and you need to write it off and declare it as a bad debt so you can clear the invoice out of your accounts receivable and reduce your net profit by its amount. All you need to do is to create one expense account for bad debt. There's no need to create one for each customer. You can track them by running an Account QuickReport. The steps below will ensure your success in writing off bad debts:

Step 1: Add an expense account to track the bad debt.

1. Click Lists on the menu.
2. Select Chart of Accounts.
3. Select the Account menu and then New.
4. Select Expense, then Continue.
5. Enter an Account Name, for example, Bad Debt.
   
6. Select Save and Close.

Step 2: Close out the unpaid invoices.

1. Click Customers menu.
2. Select Receive Payments.
3. Enter the name of the customer in the Received from field.
4. For Payment amount, enter $0.00.
5. Select Discounts and credits.
6. In the Amount of Discount field, enter the amount you'd like to write off.
7. For Discount Account, select the account you added in step 1, and select Done.
   
8. Select Save and Close.

This article outlines the steps for writing off bad debt: Write off bad debt in QuickBooks Desktop.

To run the Account QuickReport, follow the steps below:

1. Click Lists on the menu.
2. Select Chart of Accounts.
3. Locate your Bad Debt account and right-click on it.
4. Select QuickReport:Bad Debt.

In addition, you can check your customers' open balances by running the Accounts Receivable Aging Detail report. Just follow these steps: 

1. Go to the Reports menu.
2. Select Customers & Receivables.
3. Click A/R Aging Detail. 

Please let me know if you have any follow-up questions about writing off bad debts. I'm always here to help. Have a wonderful day.