If you integrate Verifactu on behalf of third parties — an accounting firm with hundreds of freelancers, an ERP with thousands of customers, a vertical POS — you already know where onboarding stalls. It is not the API. It is not the invoice format. It is a PDF.
For Verifacti to send invoices to the AEAT on behalf of a NIF, the holder of that NIF must sign a representation model. And until now, signing it required something a great many freelancers do not have at hand: a digital certificate.
Online signing removes that requirement. The holder of the NIF verifies their identity by video from their phone and signs with one click. No certificate, nothing to install, no trip to an office. This article covers how it works, what it costs, where the limits are, and how to automate it from your own product.
The onboarding bottleneck: the representation model
Verifacti does not ask its customers for each taxpayer's digital certificate. It sends the tax information to the AEAT with its own certificate, under the framework of social collaboration — specifically, under agreement 017, created to cover that figure in the context of Veri*Factu.
That avoids the worst pattern in the industry — asking every freelancer to hand over their certificate and password — but it comes with a regulatory counterpart: whenever it is not the taxpayer themselves who submits their information, the AEAT requires that taxpayer to sign a model authorising Verifacti to send tax information on their behalf. The models were published in the BOE in December 2024 (Annexes I, II and III).
The classic way to sign it is three steps: generate the PDF with the holder's details, sign it with a digital certificate and upload it to the platform. It is free and works perfectly… as long as the holder has a certificate.
And that is the problem. A huge share of freelancers have no digital certificate installed, or have an expired one, or have it on a computer they no longer use, or have no idea what a .p12 file is. Getting a new one from the FNMT means an in-person identity check at an office. Translated into your onboarding funnel: days or weeks of waiting, follow-up emails, support tickets, and customers stuck halfway through.
What online signing changes
Online signing replaces that errand with a link. You make one API call (or click a button in the dashboard) with the holder's details; the holder receives an email, verifies their identity by filming their ID document and a short selfie video, and signs the model with one click from their mobile browser.
It is an advanced electronic signature with identity verification: the check is carried out by a qualified trust service provider, not by an "I accept" checkbox. Once completed, the representation status automatically changes to Correcto and the NIF can send invoices in production, with no further action on your side.
In product terms, the difference is the one between an asynchronous errand with an uncertain ending and a flow that resolves within the same session:
- No digital certificate, no installations, no trips.
- No sign-up: the link itself identifies the signer — no username or password to remember.
- From a phone (or a computer: the process is identical).
- Minutes, not weeks — and the representation validates itself.
What the signer sees, step by step
This is the part worth knowing well, because it is what your end customer will experience and what they will ask your support team about. The full journey is six moments:
- They receive an email with an Open document button. The sender shown can be customised.
- They open the document and accept the terms: they see a summary of the sender and the modelo_representacion.pdf, and consent to the processing of their personal and biometric data.
- They verify their identity: they choose the document type and film it following an on-screen frame.
- They record a short selfie inside an oval, to confirm they are the same person as on the document.
- Automatic verification: the identity is validated within seconds and the result is shown.
- They review the model and sign with one click. They see a confirmation and can close the window.
We have published the whole journey with real screenshots of every screen in the guide Online signing of the representation model. It is a page designed so you can show it to your customer before triggering a signature, or link it from your own application to defuse questions before they reach support.
How to start a signature from your integration
A single endpoint in the NIFs management API. You pass the holder's details and their email:
curl 'https://api.verifacti.com/representacion/firma_remota/16085921K' \
--request POST \
--header 'Content-Type: application/json' \
--header 'Authorization: Bearer <USER_API_KEY>' \
--data-raw '{
"nombre": "Pablo",
"apellidos": "García Gómez",
"municipio": "Madrid",
"calle": "Gran Vía",
"numero": "43",
"email": "pablo@example.com"
}'The response contains the signing link, which is also emailed to the signer:
{
"url": "https://saas.esignanywhere.net/workstepredirector/go#..."
}The fields nombre, apellidos, municipio, calle, numero and email are mandatory: they are the data used to fill in the model before sending it out for signature. The full name on the document is the concatenation of nombre and apellidos.
If you would rather not integrate anything, the same flow is available from the Verifacti web interface, under Settings → Representation for each NIF. That is the natural route for a firm handling registrations by hand; the API is the route for anyone who wants to resolve onboarding inside their own product.
Tracking, expiry and cancellation
While signing is in progress, the representation status is Pendiente. Querying it also returns the link and its expiry date, so the signer can resume the process at any time — and you can recover the link if it gets lost:
{
"estado": "Pendiente",
"url": "https://saas.esignanywhere.net/workstepredirector/go#...",
"fecha_expiracion": "2026-09-05T09:12:44.000Z"
}The lifecycle rules are simple:
- It expires 28 days after creation. Until then, the signer can resume from the email or from the link.
- It can be cancelled at any time with PUT /representacion/cancelar/:nif or from the web interface.
- On completion, the representation turns to Correcto by itself. Nothing to upload, nothing to confirm.
- If it expires or is cancelled, a new process can be started, which is charged as a new signature.
Customisation: language, sender and link delivery
Two details that matter when the signature is triggered by your product rather than by Verifacti:
The language of the ceremony
The signing ceremony and the email are shown in Spanish by default. The optional idioma field (es or en) switches them to English.
The email the signer receives
The optional notificacion object customises the sender name, the subject and the message of the email. For many integrators this is what turns the errand into part of their own brand rather than a message from an unknown third party.
Or no email at all
The email field is mandatory, but it does not have to be the NIF holder's. If you pass an internal address of your own, your end customer receives no email from Verifacti: the API response already gives you the signing link, and you deliver it through whichever channel you prefer — your own application, your transactional email, WhatsApp. The whole errand stays inside your product.
Limits and small print
Online signing does not cover every case. These are the real limits, unvarnished:
- Individuals only. The issuing NIF must be a DNI or a NIE. Companies still sign with an entity representative certificate — which, for what it is worth, they usually do have.
- Verification uses a DNI or a passport, not the NIE card. A holder whose NIF is a NIE can still sign, but must identify themselves with their passport.
- The holder must sign in person. The verified name has to match the holder of the NIF according to the AEAT. If their accountant, their business partner or a relative signs instead, the signature is rejected and the status turns to Rechazado. This is the restriction most worth explaining up front.
- Cost: €2.90 + VAT per process, added to your next invoice. It is applied when the process is created, even if the signature is never completed, and it is not refunded on cancellation or expiry.
- A valid payment method is required. If the account has unbilled signatures pending and the charge fails, the call returns a 402 and no process is created.
And one detail that saves money: the representation model is handled once per NIF. Online signing is environment-independent, so a signature completed from a test NIF also validates that same NIF in production, even if the production NIF has not been created yet. Signing the same NIF twice is €2.90 thrown away.
Online signing or digital certificate: when to use each
The two methods coexist and neither replaces the other. The choice is fairly mechanical:
| Online signing | Digital certificate | |
|---|---|---|
| Who can use it | Individuals only (DNI or NIE) | Individuals and companies |
| What the holder needs | A phone or computer with a camera and their ID document | A valid digital certificate (.p12 or .pfx) |
| Steps | Open link, verify identity, sign | Generate PDF, sign it, upload it |
| Typical time | Minutes | Depends on whether they already have a certificate |
| Cost | €2.90 + VAT per process | Free |
The practical rule: if the holder is a company, use a certificate. If they are a freelancer who already has a certificate and knows how to use it, use a certificate — it is free. And if they are a freelancer without one, which is where most stalled registrations live, online signing turns weeks of friction into an afternoon. At €2.90, the comparison is not against the free certificate: it is against the registration that never completes.
Frequently asked questions
What exactly does the signer need?
A phone or computer with a camera and their ID document (DNI or passport). No digital certificate, no app to install, no account to create.
Can a company sign online?
No. Online signing is available only for individuals: the issuing NIF must be a DNI or a NIE. Legal entities must sign the model with the company representative certificate, by downloading the PDF, signing it and uploading it. That method is free.
The holder has a NIE — can they sign?
Yes, but they must identify themselves with their passport: the NIE card is not accepted as a verification document. In every case, the verified name must match the holder of the NIF according to the AEAT.
What happens if someone else signs for them?
The signature is rejected and the representation is not validated: the status turns to Rechazado. That is what happens when the person completing the identity verification is not the holder of the NIF — for example, if their accountant signs. A new process would have to be started with the right person, charged as a new signature.
How long does the signer have to complete the process?
The process expires 28 days after it is created. Until then they can resume whenever they like from the email or from the link, which can be recovered by querying the representation status.
How do I know the signature is complete?
The representation status automatically changes to Correcto and the NIF can send invoices in production. You can check it with GET /representacion/estado/:nif or from the web interface, under Settings → Representation.
Can it be used in the test environment?
Yes, and it works the same way — at the same cost. On top of that, since the model is handled once per NIF, a signature completed from test also validates that NIF in production, even if the production NIF does not exist yet.
Does it work for TicketBai too?
No. Online signing of the representation model is for Veri*Factu. In the Basque Country, certificate and representation management for TicketBai follows a different path, which we explain in the FAQ.
Where can I see the full process before triggering it?
In the guide Online signing of the representation model, with real screenshots of the eleven screens the signer goes through. And if you want to integrate it, the endpoint details are in the NIFs management API documentation.