Becoming autónomo

Key facts

The two registrations — and why the order matters

Registration one: the tax office. You file an alta censal with the AEAT on Modelo 036, declaring your activity (its epígrafe IAE), your address and your tax obligations. Since 3 February 2025 the simplified Modelo 037 no longer exists — Orden HAC/1526/2024 folded its simplified path into the 036 itself. Many top-ranking guides still recommend "the shorter 037" — any checklist that treats it as a live form is out of date.

Registration two: Social Security. You file your alta in RETA through the Import@ss portal. Under RD 84/1996, art. 32, the alta can be submitted up to 60 calendar days before the day you begin trading — a useful window for lining the paperwork up in advance. Do not invert the order: an alta filed after you have started is fuera de plazo — lost tarifa plana, back-charged quotas and a possible surcharge.

Both registrations must exist before your first invoice — the one rule with no workaround.

What you pay: the tramo system

Since January 2023 (RDL 13/2022) your monthly quota follows your real net income (rendimientos netos) across 15 income bands — the tramos. You forecast your income, pay the band’s quota, and Social Security regularises the difference after the tax year closes.

For 2026 the tables did not change: RDL 16/2025 prorogued the 2025 tables for the whole of 2026 (only the maximum bases of the top bands were touched). In round numbers:

Treat every figure as approximate: the MEI surcharge (Mecanismo de Equidad Intergeneracional) rose to 0.9% in 2026, so exact quotas sit slightly above the nominal table values. For your own number, use the official Import@ss quota simulator.

The tarifa plana for new autónomos

If you have not been in RETA in the previous two years (three, if you already used the discount), your first 12 months are charged at the tarifa plana — a flat €80 per month nominal, ≈€88.64 once the 2026 MEI is added. If your net income in that first year stays below the SMI (the minimum wage), you can extend the flat rate for a further 12 months by applying before the first period ends. Afterwards you move onto the income bands like everyone else.

Autónomo or a company?

For most freelancers starting out, autónomo is the cheaper and faster structure: no capital, no notary, no accounts to deposit. The comparison changes when revenue grows, when you take on partners or when liability matters — that fork is covered in setting up an S.L. company.

How to register: step by step

1. Get your NIE — and ideally a digital certificate. The NIE doubles as your tax number; the certificate (or Cl@ve) is what lets you file both altas online instead of queueing.
2. File Modelo 036 with the AEAT. Declare the alta censal, pick the epígrafe IAE for your activity and state your IVA and IRPF obligations. Do this before you begin trading.
3. File your alta in RETA through Import@ss. You can submit it up to 60 days before your start date; the alta must never come after the activity has begun.
4. Set your contribution. Forecast your net income to land in a tramo, or apply the tarifa plana if you qualify as a new registration.
5. Start invoicing. Only once both altas exist; from here your obligations are quarterly tax filings.

The filings are free and, with a certificate, doable in an afternoon. What a professional adds is judgment — the right epígrafe, income forecast and deductions. That trade-off is the subject of working with a gestor.

⚠ Scams to avoid

• ✗ Paid "autónomo registration" packages sold as mandatory. The Modelo 036 and the RETA alta are free official filings. Paying a service for convenience is legitimate — paying a claimed "official registration fee" is not.
• ✗ Guides selling the Modelo 037 route. The form was abolished on 3 February 2025. Any paid course or template built around the 037 is recycling dead paperwork.
• ✗ "Register later, invoice now" advice. Invoicing before the alta is not a grey area: it is an alta fuera de plazo, with lost discounts and back-charged quotas.