Invoice Numbering: Sequential Series and Common Mistakes
Why numbering matters
The Invoicing Regulation (RD 1619/2012) requires invoices to have sequential numbering within each series, with no gaps or duplicates. It is one of the requirements the Inspectorate checks most.
What a series is
A series is a set of invoices with its own numbering. You can have a single series or several depending on your organisation. Within each series, numbers must be consecutive.
When to use several series
- Corrective invoices: must go in a specific series.
- Different establishments or points of sale.
- Tickets and simplified invoices versus full invoices.
- Invoices issued by the recipient or by third parties.
What matters is not how many series you have, but that each is sequential and gap-free.
Common mistakes
- Numbering gaps from cancelling invoices instead of correcting them.
- Duplicating numbers by using several books or programs.
- Restarting numbering mid-year without control.
- Mixing corrective invoices with the ordinary series.
With RegulaKit numbering is managed automatically and sequentially per series, avoiding gaps and duplicates. Discover it on our platform.
Conclusion
Sequential, well-organised numbering by series avoids problems with the Tax Agency. Automating it is the best way to guarantee no gaps or duplicates.
Frequently Asked Questions
Must invoice numbering be sequential?
Yes. Within each series numbers must be consecutive, with no gaps or duplicates.
Can I have several invoicing series?
Yes. You can use several series, for example for corrective invoices, establishments or tickets.
Do corrective invoices have their own series?
Yes, they must be issued in a specific corrective series.
What if I cancel an invoice?
You must not leave a gap; the correct way is to issue a corrective invoice, not delete the number.
Can I restart numbering each year?
Yes, it is common to restart per financial year, as long as it is sequential within the year.