How does invoice numbering work?

Invoice numbering can be managed in two ways :

• Automatic numbering, recommended and enabled by default, which avoids renumbering and guarantees a consistent sequence without errors.
  Invoices to be validated remain without a number and carry a "draft" watermark. The final number is assigned automatically when the invoice is transferred to the sales journal.
  To enable this mode: go to "Configuration > General options > Billing" and check the option "Number invoices when updating the sales journal". Log out and log back in to apply the change.

• Manual numbering: each invoice to be validated receives a provisional number. In case of deletion or modification, renumbering is necessary. A "Renumber" button is available on the invoices-to-validate page: it updates the selected invoices and all following invoices.
  The invoices-to-validate page has a "Duplicate" column that identifies invoices whose number is already used. If an invoice to be validated has "Duplicate" checked, you must renumber it using the "Renumber" button.
  To avoid numbering issues, a check is performed during invoice validation to identify duplicates or gaps in billing.

In both modes, proposed numbering can comply with a custom format, such as yymm0000 for a two-character year and month followed by a number reset every year or every month, or yynnnnnn for a two-character year followed by a number that never resets. You can contact support to set this up.

Numbers of validated invoices are final and can no longer be modified. In case of a billing error, you can issue a credit note and create a new invoice.

Invoices must respect chronological order: you cannot validate an invoice whose date is earlier than that of an invoice already validated and issued by the same company. However, you can prepare invoices with any date; you will simply need to correct invoice dates before validation.