Once an invoice has been sent to the accountant, it typically cannot be adjusted. This is because an invoice can only be sent to the accountant once, meaning any changes would not be recorded in the accounting system.

However, to still adjust the invoice, you can change a setting. In the invoice overview, go to "More actions" > "Settings" and set the "Modify invoice" option to "Always allow."

Don't forget to manually inform the accountant of the change. After making the adjustment, it's best to revert the setting to prevent future errors.

Modifications to an invoice after it has been sent to the customer are not allowed by tax authorities.

To adjust an invoice, you must first offset the original invoice with a credit note and then create a new, corrected invoice.