If a customer is not going to pay an invoice and it needs to be written off, you can Stop Collection from the Invoice Actions dropdown at the top right of the invoice details page. This action will move the invoice to a Failed state and removes the amount from the customer's account balance. Note that failing an invoice will create a corresponding write-off credit invoice, bringing the failed invoice's balance to zero. Stopping collection will also stop the dunning cycle, stopping all automated dunning emails and automated payment retries (automatic collection only).
Once an invoice is failed, it cannot be reopened. This is also the case for manual collection invoices, due to the fact that the write-off credit invoice exists.
Please Note: Stopping collection (failing) on an invoice will not automatically cancel the related subscription. The subscription needs to be canceled separately in order to stop the subscription from billing again.