How to become autónomo in Spain: a practical step-by-step guide

1. Prepare decisions before opening the forms

Gather DNI or NIE, NUSS, digital certificate or Cl@ve, IBAN, address, start date and expected net returns. Describe what you sell, to whom and from where, then map it to IAE for Hacienda and CNAE for Social Security.

Do not copy another freelancer's code just because both work on laptops. Consulting, software and online education can create different obligations.

• Separate Spain, EU B2B, EU B2C and non-EU customers.
• Note premises, staff, rent and payments subject to withholding.
• Check ROI/VIES before the first qualifying intra-EU B2B operation.

2. Set the real date and coordinate both registrations

RETA registration can be arranged up to 60 days in advance. Hacienda and Social Security dates must match and be complete before or on the start day. Late registration can lose contribution benefits and create surcharges.

Do not use the first bank payment as the only signal. If work or preparatory business purchases already began, establish a defensible date.

• Modelo 036 configures tax obligations.
• Importass handles RETA, base, mutual insurer and debit account.
• Keep both receipts and compare dates.

3. Configure Hacienda with Modelo 036

Modelo 037 was abolished on 3 February 2025. Modelo 036 records activity, IAE, address, IVA, IRPF, withholding and EU operations.

Read the resulting obligations as a calendar: an assigned return may still be expected after a quarter with no revenue.

• Do not select IVA or withholding by guesswork.
• Keep PDF, CSV and effective date.
• Update the census when the business changes.

4. Complete RETA through Importass

You will need NUSS, identity, date, activity, address, contact details, expected net returns, mutual insurer, base and IBAN. Request the reduced contribution during registration if eligible.

The forecast can be updated when the business changes. Keep liquidity for annual regularisation.

• Choose a base within the expected band.
• Download proof of registration.
• Check the first debit and benefit applied.

5. Example: a consultant starting 1 September

Anna will advise Spanish companies and one French company. Before 1 September she chooses IAE, requests ROI when required, files Modelo 036 and registers in RETA with the same date. She requests the reduced contribution during registration.

On day one she creates an invoice series, separates customers by territory, saves VIES evidence and opens an expense archive. She does not wait until October to discover assigned returns.

• Week one: verify registrations, obligations and first invoice.
• Monthly: reconcile invoices, expenses, bank and platforms.
• Before quarter-end: check returns, deadlines and cash reserve.

6. Keep an evidence file

Retain Modelo 036, RETA proof, mutual-insurer choice, forecast, ROI/VIES evidence and the reasoning behind activity classification. This file explains why the initial obligations were chosen.

• Modelo 036 PDF and CSV.
• RETA registration proof.
• Tax calendar and invoice ledger.
• Questions requiring professional review.