mellomInvoice

Mellom products

mellomSimple technology for accommodation and small businesses Mellom HostYour booking website, built to measureAvailable Mellom GuestOnline check-in and SES.Hospedajes registrationAvailable Mellom InvoiceInvoices for any freelancer or businessSoon

In testing · Waiting list open

One VERI*FACTU engine. Two ways to use it.

Connect it to your invoicing software with Invoice Engine, or invoice directly with Invoice App. Both run on the same engine, built for Spain’s new invoicing rules.

Invoice EngineThe API for your invoicing software Invoice AppThe app for freelancers and small businesses
Join the waiting list What is VERI*FACTU?

Free for a whole year if you sign up during the testing period. For Spain’s common tax territory: the Basque Country and Navarre have their own regional tax rules.

Invoice Engine

VERI*FACTU inside your software, without rebuilding it.

Your software keeps creating invoices the way it does today. As it issues each one, it passes it to Engine through the API, and Engine does what the rules require: it assigns the number, chains it to the previous one, generates the QR code and sends the record to the Spanish Tax Agency (AEAT).

01

Your software sends the invoice

One API call with the invoice data, at the moment it is issued.

02

Engine validates and records it

It checks the data, assigns the number and computes the hash that chains it to the previous one.

03

It sends it to the Tax Agency

Queued and at the pace the AEAT sets, with automatic retries if something fails.

04

Your software gets the result

The number, the QR code to print on the invoice and the status of the submission.

For your technical team

One call per invoice.

A REST API with an OpenAPI contract. Every request carries an idempotency key: if your software repeats it after a network failure, it gets the same invoice back, never a duplicate.

  • Separate API keys for testing and production
  • Amounts as exact decimal text, no rounding errors
  • Corrective invoices and cancellations as linked records
Ask for test access 
# Illustrative example
POST /v1/issuers/{id}/invoices
Idempotency-Key: 7c9e…4d07

{
  "invoiceType": "F2",
  "description": "Consultation",
  "lines": [{
    "description": "Consultation",
    "quantity": "1",
    "unitPrice": "41.32",
    "taxRate": "21"
  }],
  "externalId": "caja-3:88412"
}

# → 201 Created
{
  "numSerieFactura": "F2-004812",
  "importeTotal": "50.00",
  "qr": { "url": "https://…" },
  "record": {
    "huella": "3F9A…C21E"
  }
}

What it takes care of

Built to integrate, and to handle volume.

The hard parts of VERI*FACTU (the chain of records, the AEAT’s flow control, the retries) stay on our side.

REST API with an OpenAPI contract

A published, versioned contract, so you know exactly what to send and what you will get back.

A separate test environment

Try your integration with test keys and without touching real data. Production is kept apart.

Retries without duplicates

Repeating a request with the same key returns the same invoice. And if the content changes, Engine rejects it.

Peaks in volume

Hundreds of invoices in one morning? Engine queues them and sends them to the AEAT at the pace it allows, without keeping your software waiting.

Several issuers in one account

A group with several companies, or software with many customers: each issuing tax ID (NIF) has its own chain of records.

Webhook notifications

Your software hears about every change of status (accepted, accepted with errors, rejected) without having to ask.

Who is Engine for?

  • Software makersPOS, ERP or back-office software that needs to comply with VERI*FACTU without building and maintaining its own tax module.
  • Companies with their own invoicingChains, clinics or franchises that invoice from their own system and issue many invoices every day.
  • Agencies and integratorsThose who build custom software for their clients and need a reliable tax component they don’t have to rewrite.

Invoice App

Invoice in seconds, with no rules to learn.

For freelancers and small businesses in any sector: a workshop, a tutoring centre, a shop or a place to stay. You create the invoice, your customer gets it by email and the record reaches the Spanish Tax Agency.

  • Invoices in seconds
  • Customers and products
  • Automatic numbering
  • Sent by email with its QR code
  • Basic reports
  • Nothing to install
Sign me up for Invoice App
Record sentto the Spanish Tax Agency
01

Add your customers and products

Just once. After that, you pick them from a list each time you invoice.

02

Create the invoice in seconds

Numbering, VAT and totals are worked out for you. You check it and issue it.

03

It’s sent and recorded

Your customer gets it by email with its QR code, and the record reaches the AEAT.

Real screens

This is Mellom Invoice today.

Screenshots of the app in development, as it looks on a phone: signing in, your issuer record and your customers. The invoice screens, the PDF and the QR code will come in future versions.

  1. Mellom Invoice sign-in screen on a phone, in Spanish: the banner “SIN VALIDEZ FISCAL · Entorno local de desarrollo · No se remite nada a la AEAT” (no tax validity, local development environment, nothing is sent to the AEAT), the title “Entrar en Mellom Invoice”, the email and password fields and the Entrar (sign in) button.
    1

    Sign in to your account

    Each organisation has its own accounts, and whoever runs it gives access to the team.

  2. Issuer record of the demo issuer “Alba Ficticia Demo”, with a test tax ID and a fictional address, in Spanish: its status, “Activo en pruebas locales” (active in local testing), the notice that nothing is sent to the AEAT and the set-up steps still pending.
    2

    Your issuer record

    Your tax details and how the set-up is going: what is ready and what is missing before you can invoice.

  3. The issuer’s customer list, in Spanish: the explanation that every invoice and every draft keeps a copy of the customer’s details, the “Solo datos de prueba” (test data only) notice, the Nuevo cliente (new customer) button and the demo customer “Taller Sintético Lumen (demo)”.
    3

    Your customers

    You add them once. Every invoice keeps a copy of their details, so changing a customer never alters what you have already issued.

  4. Record of the demo customer “Taller Sintético Lumen (demo)”, in Spanish: the “Solo datos de prueba” (test data only) notice, the note “Tus borradores no cambian” (your drafts don’t change) and the start of their details, with a test tax ID.
    4

    Each customer’s record

    Their details, with clear notes on what changes and what doesn’t when you edit them.

Real screenshots of Mellom Invoice in a local development environment, with demo data: fictional names and test tax IDs. That’s why they carry the “SIN VALIDEZ FISCAL” (no tax validity) banner; nothing you see has been sent to the AEAT. The app is in Spanish.

VERI*FACTU

The new way to invoice in Spain, in brief.

The regulation on invoicing systems (Royal Decree 1007/2023) requires invoicing software to guarantee the integrity and traceability of every invoice. Under VERI*FACTU (Spain’s verifiable invoicing system), each record is sent to the Spanish Tax Agency (AEAT) the moment the invoice is issued.

  • Chained recordsEach invoice generates a record with a hash, a digital fingerprint that depends on the previous one: nothing can be deleted or altered without it showing.
  • QR code on the invoiceYour customer can check it on the AEAT website just by scanning the code.
  • Automatic submissionWith Engine or with App, Mellom Invoice takes care of sending the records. You just invoice.
1 January 2027Companies (those subject to corporate income tax).
1 July 2027Everyone else required to comply, including freelancers.

Deadlines set by Royal Decree 1007/2023, as in force in September 2026.

Testing period

Sign up now and use it free for a whole year.

Invoice Engine and Invoice App are in their testing period. Anyone who joins the waiting list during testing gets their first year free.

1You sign up

Leave us your email and tell us what you are interested in: Engine, App or both.

2We let you know

Today the engine is in testing and does not issue real invoices yet. We will write to you as soon as you can get in.

3A year free

Because you signed up during testing, your first year costs you nothing.

After that year: Invoice App will have a small monthly fee; Invoice Engine, a price based on invoice volume. We will publish the prices before opening.

Join the waiting list

Waiting list

Be one of the first to use Mellom Invoice.

Tell us which product you are interested in and we’ll let you know as soon as you can try it. If you sign up now, your first year is free.

  • Just one messageWe’ll write to you when you can get in. No newsletters.
  • Planning to integrate Engine?Tell us which software you use and how many invoices you issue a month: a person will reply.
  • Made in SpainDesigned for Spanish regulations from day one.

We will only use your details to notify you and reply to you. More information in the privacy policy.