You can only delete an invoice in its draft stage.
Note: Deleting is not the same as voiding. Voiding an invoice turns allocated payments into credit and doesn't erase the invoice, but rather archives it for audit and fraud prevention purposes. Click here to learn how to void an invoice.
Go to Accounts > Invoices
OR access via your Calendar:
Click on the booking, then the client name and navigate to the Accounts tab
Select and open the draft invoice you want to delete
Delete the draft invoice, by scrolling to the bottom of the invoice and clicking Delete on the bottom left of the invoice.
Go to Accounts > Payments
Select the client account from which you'd like to delete a payment
You can either delete the whole payment, or select allocated payments to delete by clicking the red bin icon next to the invoice the money was allocated to.