You sent an Invoice for $300.00. That customer has since gone bust but your debtor reports still shows a debt of $300.00.
First you must check with your accountant/ auditor about the legislation’s in your local area. Some countries only allow you to write-off a debt after a certain period. Once you are certain you can write it off, you call for a New Receipt, but instead of selecting your bank account to post the receipt , select a “Bad Debts Written Off” account.