Starting your freelance journey in Spain?
Whether you’re opening your first client project or finally turning your side hustle into your main job, this guide walks you through how to register as an autónomo with the Tax Agency (AEAT).

We’ll cover everything: the forms you need (Model 036 or 037), how to choose your activity code, when to file, and what happens once you’re in the system.

But more importantly, you’ll understand what it really means to “become autónomo” - not just filling in forms, but officially taking the first step toward building something of your own.

Many freelancers say this part feels confusing the first time. That’s normal. The goal here is to make it simple, so by the end of this guide you’ll know exactly what to do, when to do it, and how to stay compliant from day one.

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Q&A

Do I need to register before sending my first invoice?
Yes. You must inform the Tax Agency before starting your activity.

Does it cost money?
No, registering with AEAT is free.

Can I do it online?
Yes, through AEAT’s online portal (Sede Electrónica) using Cl@ve PIN or a digital certificate.

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What “registering as autónomo” means

Registering as autónomo means officially telling AEAT that you’re starting a professional or business activity on your own.
Once registered, you’re added to the Censo de Empresarios, Profesionales y Retenedores - the official list of business operators in Spain.

This activates your tax duties:

• Issuing invoices with the correct VAT (IVA) and income tax (IRPF).
• Filing quarterly and annual tax forms.
• Keeping accounting records.

You’ll also need to register with Social Security (RETA) to start paying your monthly contributions. That’s a separate but required step.

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Step 1 - Decide when and why to register

You must register if you plan to work regularly as a freelancer and issue invoices.
Occasional, one-off work may not require it, but as soon as your activity is continuous, registration becomes mandatory.

Why it matters:

• You can legally issue invoices.
• You can deduct business expenses.
• You avoid fines or retroactive payments.

You can pre-register up to 60 days before your start date, but you must complete it before or on your first day of work.

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Step 2 - Choose and submit the correct AEAT form

What to fill in

You’ll need to provide:

• Personal details: name, NIF/NIE, address, contact info.
• Activity code (IAE/CNAE): defines what you do professionally.
• Business location: your work address or home office.
• Tax regime:
  • VAT (IVA): whether you charge it or are exempt.
  • IRPF: whether you apply income tax withholdings.
  • Regime type: direct estimation or modules (objective estimation).
• Start date: when you begin activity — it sets your filing deadlines.
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Step by step - AEAT registration (model 036): pick your IAE epígrafe and tax regimes

The takeaway: model 036 via Censos WEB is your tax “on switch”.

Check here our YouTube video-tutorial for free.

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Enter Censos WEB and file model 036. In one form you will:

• Declare your activity start date.
• Choose your IAE epígrafe (activity code).
• Pick your VAT (IVA) and IRPF regimes.

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IAE epígrafe (activity code)

It’s the label for your job. Designer, developer, photographer, café owner - each has a code. Most freelancers won’t pay IAE until they pass €1,000,000 turnover, but the code is still mandatory for registration.

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Let´s imagine you want to register as an IT developer 👩🏻‍💻: in "Buscador de actividades" you´d type 763 and press "Seleccionar".

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Once you´ve already chosen your activity you have to select where you carry out your activity:

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VAT (IVA) regime

• General regime: you add VAT to invoices and deduct VAT on business expenses.
• Special cases: for example, “recargo de equivalencia” (a retail surcharge where the supplier charges extra and the retailer doesn’t file VAT returns).

Most service freelancers use the general regime.

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IRPF method

• Direct estimation (simplified): the default for most freelancers. You report real income and real expenses.
• Modules (objective estimation): only for certain activities and limits; it uses fixed amounts instead of your real numbers.

If unsure, contact us.
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When you finish filling the information press "Validate tax record" and then "Sign and send".

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Once sent, congrats! you are one step closer 🧡.

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What happens after you register

Once accepted, you’re officially in AEAT’s business census.
From that day:

• You must issue invoices with your NIF, invoice number, date, and tax breakdowns.
• You start filing regular tax returns such as:
  • Model 303: quarterly VAT
  • Model 130: quarterly income tax payments
  • Model 111/115: if you retain IRPF on rent or employees
• You keep simplified books of income and expenses.

Next, register with Social Security (RETA) within 60 days before or on your start date to activate your contributions.

Failing to register properly can lead to fines and retroactive payments.
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Bottom line

Registering as autónomo with Spain’s Tax Agency is the essential first step to legally work as an independent professional. The process is straightforward: first, obtain a digital certificate or activate your Cl@ve PIN to access official online services. Then, complete and submit Form 036 or 037 on the AEAT website before your first day of activity. Once this is done, you must also register with the Social Security system (RETA) to formalize your self-employed status.

Completing these steps correctly ensures that your invoicing, expenses, and tax obligations are properly set up from the beginning, helping you avoid administrative problems or penalties in the future