We do this manually at this point of time, until we build this feature. It is not possible to cancel/void or amend an invoice directly in ChargeBee at this time.
If you do need to have an invoice removed, please send a request to firstname.lastname@example.org with the invoice and site details.
This feature is in our product road map and will be implementing it.
Note: Only unpaid invoices can be deleted at the moment. Paid invoices cannot be deleted.
How is this feature coming along?