To register as autonomo, you need documents for two separate registrations: one with the Tax Agency (Hacienda) and one with Social Security. You do them in that order.
Here's the full list for each.
Documents for AEAT registration (Tax Agency)
This is the first registration. You submit either Modelo 036 or Modelo 037. For the full registration process, see our step-by-step guide to registering as autonomo.
Which form do you use?
For most autónomos: Modelo 037. It's the simplified version. If you're a freelancer, consultant, designer, or developer, 037 is enough.
Use Modelo 036 if:
- You import or export goods
- You apply for VAT exemption on intra-EU transactions
- You're registering as a partnership or business entity (not a sole trader)
- You have a special tax regime
If you're not sure, use 037.
What you need:
- DNI (Spanish nationals) or NIE (foreigners): your tax identification number. Must be valid.
- Modelo 037 (or 036 if applicable): available at any AEAT office or online. You fill it in during registration, not in advance.
- IAE code: the activity code that classifies what you do. You select this during registration. Common codes: 763 (freelance technical services), 722 (software and IT), 741 (accounting).
- Business address: your home address is fine.
- Start date: the date you intend to begin working as autonomo. Register before your first invoice.
You can register in-person at any AEAT office or online at sede.agenciatributaria.gob.es using a digital certificate or Cl@ve.
Documents for RETA registration (Social Security)
Once your AEAT registration is complete, you register with Social Security.
What you need:
- DNI or NIE: same document as above.
- Completed Modelo 037 or 036: the copy from your AEAT registration, showing your activity code and start date.
- Spanish bank account (IBAN): your monthly Social Security quota is direct-debited. Must be a Spanish IBAN or a bank in the SEPA zone.
- Contribution base selection: you declare your estimated monthly net income for the year. This sets your Social Security quota. You can adjust it up to 6 times per year.
- Mutua: the insurer that covers you for sick leave and accidents. You choose one at registration. Main options: Asepeyo, Fremap, Mutua Universal. All offer similar coverage.
Register in-person at any INSS office, or online via Import@ss at importass.seg-social.es.
If you're a foreigner: what changes
EU citizen (German, French, Italian, etc.):
You can use your EU national ID or passport instead of a DNI. You still need an NIE to register. Get it at a Comisaría de Policía or through your country's consulate. The NIE is the tax ID that appears on all your invoices.
Non-EU citizen:
You need a TIE (Tarjeta de Identidad de Extranjero), your Spanish residency card. You also need a valid work authorisation that permits self-employment. A general work permit (cuenta propia), Digital Nomad Visa, or long-stay visa with work authorisation all qualify.
Without the right residency and work authorisation, you cannot legally register as autonomo.
Online registration: what you need extra
If you want to register without going in-person, you need one of two things:
Certificado digital (digital certificate): A digital ID from the FNMT (Fábrica Nacional de Moneda y Timbre). Free. Valid for 4 years. Apply at fnmt.es, then verify your identity in-person at any AEAT office or Registro Civil. After that, download and install the certificate in your browser.
Cl@ve: A government identity system that lets you log in with an SMS code. Easier to set up. Works for most autonomo processes, though some advanced procedures still require the digital certificate.
Both are free. If you're going to be autonomo long-term, get the digital certificate. You'll use it for quarterly tax filings, Social Security changes, and official correspondence for years.
Full checklist
AEAT (Tax Agency)
- DNI or NIE (valid)
- Modelo 037 (or 036 if your situation is complex)
- IAE activity code selected
- Business start date confirmed
- Home or business address
RETA (Social Security)
- DNI or NIE
- Copy of completed Modelo 037/036 from AEAT
- Spanish/SEPA bank account IBAN
- Estimated monthly net income (for contribution base)
- Mutua selected
For online registration (either step)
- Digital certificate (certificado digital) or Cl@ve active
For foreigners:
- NIE (EU citizens: from Comisaría de Policía)
- TIE + valid work authorisation (non-EU citizens)
One important timing note
Your start date at AEAT should match the date you begin working, not the date you registered. If there's a gap, you may owe back-payments or face a penalty for late registration.
Register before you invoice. In-person, it takes one to two days. Online, it can be done in a morning.
What happens after you register
Once both registrations are complete, you're officially autonomo. Your monthly Social Security quota starts the following month. In 2026, the tarifa plana (reduced rate for new autónomos) is €88/month for your first 12 months, regardless of income.
Your first quarterly tax return (Modelo 130 for income tax, Modelo 303 for VAT if applicable) covers the quarter in which you registered.
If you want someone to handle the full registration for you and stay on top of your quarterly filings, deductions, and Social Security changes, renn does it for you. Most clients are registered within 24 hours.
