Once an invoice is closed, the invoice amount cannot be adjusted by editing the invoice itself. If the balance of a closed invoice is incorrect, a credit note can be created to credit an overcharged amount or another invoice can be generated to invoice an undercharged amount.
Credit notes and adjusted invoices can be created to credit or adjust the balance of a closed invoice in the following ways:
by processing an adjustment timesheet in an invoice batch (for timesheet-based invoices only)
by using the Credit Rebill process
by creating a manual credit note to credit a manual invoice by creating an ad-hoc manual credit note.
Each of these methods is described below.