You can cancel an invoice as long as the payment has not been made and the payment status is 'Unpaid'. 

Here's how you can cancel an unpaid invoice: 

1. Head to 'Billing' > 'Sent Invoices'.

2. Click on the ellipses icon (...) corresponding to the invoice you wish to cancel.

3. Select 'Cancel Invoice'.

When cancelling an invoice, an adjustment will be automatically passed to reflect the revised opening balance on the child's account.

All cancelled invoices can be viewed in the 'All transactions' tab. The status of the invoice will be displayed as 'Cancelled'.