Where there is a blue hyperlinked invoice number, clicking on it opens the invoice pop-up. This contains not just the invoice detail but the associated payment also.
These links can be found throughout the client card and in reports such as the invoice log.
Void an invoice
Open the relevant invoice pop-up
Click "Options" and select "Void"
Click continue in the confirmation pop-up.
A voided invoice appears in the client card but it's total value is £0.00.
Note
An invoice cannot be voided if it has a payment taken via the payment integration (e.g. online, payment link, integrated card terminal) OR payment from account money.
Voiding an invoice CANNOT be undone.
Before voiding, it might be better to refund the invoice and start again.