The invoicing software that will not let you issue a bad invoice
Series that do not tread on one another, numbering with no gaps, corrective invoices that genuinely correct, and a chained record with a hash and a QR code from the very first invoice. All of that is already in place: you write the item and the amount.
Six things the program decides, not you
Invoicing is easy until the first returned payment, the first customer who pays at 90 days or the first inspection. These six are the ones that head off the shock.
Series that do not tread on one another
Each type of document starts life with its own series — F for facturas, P for presupuestos, A for albaranes, R for rectificativas — and the company can change them. Behind it there is a unique index on company, series and number, so two invoices cannot share a number even if they are saved at the same instant.
Sequential numbering, and a warning if a number is missing
If you tick that the series restarts each year, the year is attached to the code — F26-0001 — and the count begins again in January without touching the documents already issued. And a screen checks every series and tells you which numbers are missing, while you can still remember what happened.
Corrective invoices, not deleted invoices
An issued invoice is not deleted: it is corrected. The corrective invoice comes out in its own series, points back to the original and is recorded just as it was. It is the only way to put right a mistake without leaving a gap you have to explain later.
Your template, your logo, your columns
Logo — in SVG too — colours, typeface, margins, row density, which columns appear on the lines, a footer with your payment details, page numbers and even the total written out in words. With a live A4 preview as you change it, and a different template for each type of document.
The PDF and the customer's link
The PDF is generated on the server by printing the very same A4 sheet you see on screen, so it cannot drift away from the design. And every document has a private link with which your customer views it, prints it and — if it is a quote — accepts it, with no account and no password.
VeriFactu from the very first invoice
A SHA-256 hash chained to the one on the previous record, and the AEAT's validation QR code, on every plan and on the free one too. How it works and when it becomes compulsory is set out on the VeriFactu page.
Screenshot of the ERP: six things the program decides, not you
It is the small things that eat the time
None of these things appears in a brochure and all of them turn up in your first week of invoicing for real.
- A discount on each line with the gross amount struck through, which carries over when you duplicate, convert and correct.
- Split due dates: you type «30/60/90» and the invoice is collected in three instalments, with the odd cent placed so that the total adds up.
- Partial payments: each payment is a row of its own, and the invoice's status comes out of the total, never touched by hand.
- IRPF withholding, the equivalence surcharge and suplidos (disbursements made in the client's name), all in the same form, with no separate templates.
- VAT, IGIC or IPSI depending on where you are taxed: a Canary Islands company sees IGIC rates, not VAT ones.
- The document's timeline: created, sent, opened by the customer, registered and paid.
Five documents, and what each one is for
The most expensive confusion in Spanish invoicing is using a pro forma invoice as though it were an invoice. This is what each document does, and what it does not.
| Document | What it is for | Does it have tax consequences? |
|---|---|---|
| Quote | To offer a price before doing the work. It is accepted or rejected, and expires on its own once its validity date passes. | No |
| Delivery note | To put on record what has been delivered. Several delivery notes for the same customer are grouped afterwards into a single invoice. | No |
| Pro forma | To tell a customer or a customs office the amount in advance. It looks like an invoice and it is not one. | No |
| Invoice | The document that makes the tax chargeable and that goes into the record books and into modelo 303. | Yes |
| Corrective | To correct or cancel an invoice already issued, with its own series and a reference back to the original. | Yes |
All five convert into one another without retyping the lines: a quote becomes an invoice or a delivery note, keeping the series you configured and the payment terms agreed with that customer.
Series and numbering: why this matters so much
The law requires invoices to be numbered sequentially within each series. It sounds like a formality until a number is missing: then you have to explain what happened to that invoice, and the usual explanation — «la borré porque estaba mal», I deleted it because it was wrong — is precisely the one that will not do.
Cairos deals with it underneath. The number is not typed in: the program assigns it the moment the document stops being a draft, and the database has a constraint that stops two documents belonging to the same company from sharing a series and a number. It is not a check you can slip past by saving twice from two tabs.
There is also a gap check for each series. It fixes nothing — nothing can be fixed without inventing documents — but it warns you. And drafts do not plug a gap: if number 7 is missing and there is an unissued draft, number 7 is still missing.
Restarting the numbering each year
Plenty of people want to start again at 1 each January. Cairos does it by attaching the year to the series code: F26-0001 and F25-0001 are different series, so the count starts over on its own and sequential numbering is protected exactly as before. What governs it is the document's date and not today's, so a straggling invoice dated December stays in the previous year's series, which is where it belongs.
Correct instead of deleting
When an invoice that has already been issued is wrong — the wrong amount, the wrong customer, a service that in the end was never provided — the way out is not to delete it. It is to issue a factura rectificativa, a corrective invoice that points back to the original and undoes whatever needs undoing.
In Cairos the corrective invoice is created from the original at the press of a button, inherits its lines and its discounts, comes out in its own series and is written into the chain like any other. In the books and in modelo 303 it goes in with a negative sign, so the quarter balances with nothing further to do.
What it does not do yet: correct only the difference. Today a corrective invoice is raised against the whole invoice; if what you want is to correct fifty euros on an invoice of three thousand, the full corrective invoice is issued and you invoice again. It is on the list of what comes next.
Sending the invoice and knowing whether it has been opened
Every invoice, quote, delivery note and pro forma invoice has a private link. You pass it to the customer and they see the document in your own template, print it or save it as a PDF, and if it is a quote they accept or reject it from there. They need no account, and the link is not indexed by search engines.
The system counts how many times that link is opened, so before you ring a customer to chase them you know whether it reached them and whether they looked at it. That, along with the activity log, the email queue, the VeriFactu record and the payments, comes together in a single timeline inside the document.
Email has an outbox of its own, with templates for each type of document, warnings when a variable is misspelt, sender settings that use your domain's DNS records, and the PDF already generated on the server and attached. That said, let us be clear: the sending provider is still to be connected. Today the email gets prepared and sits in the outbox, or the draft opens in your own email program. That is the only thing standing between this screen and working fully, and we would rather say so here than let you find out on day one.
What this module does not do yet
A short, honest list, because any one of these four things might be exactly the one you need:
- Factura-e in XML for public administrations. If you invoice a town council and they ask you for the file for FACe, Cairos does not generate it today. It is on the roadmap.
- Taking payment for the invoice online. The portal displays the document, it does not collect on it: there is no payment gateway connected.
- Invoicing in another currency or another language. Documents come out in euros and in Spanish.
- An overall discount on the total. Line-by-line discounts are there; the one applied at the foot of the invoice is not, yet.
Everything else described on this page works today and can be tried on the free plan, which asks for no card.
From nothing to your first invoice
Enter your details
NIF, address and logo. That is enough for a correct invoice to come out.
Choose your series
The code, whether it restarts each year, and how many digits the number has.
Issue it
Customer, lines and due date. The hash and the QR code generate themselves.
Pass it to your customer
A downloaded PDF or a private link, and from then on you can see whether they have opened it.
Issue your first invoice in five minutes
Free plan forever, no card needed.
Frequently asked questions
Invoice as though you had already been inspected
Series, numbering and the chained record are things you only miss once it is too late. In Cairos they come already set up.
No lock-in · VeriFactu included · Support in Spanish