My invoice does not have an invoice number

You must first set the invoice to the status "due".

As long as the invoice is still open, further items are added to this invoice, e.g. by the date check. As soon as you decide that you want to send the invoice now, you set it to “due” in one or more invoices using the series function and then the invoice number and the current date are automatically inserted.

Keywords: no invoice number, missing invoice number, no invoice date, invoice status