Tax Agency registration, mandatory content, IRPF withholding and tax obligations step by step.
If you are a freelancer in Spain, invoicing correctly is not optional — it is one of your most important tax obligations. And it is not just about putting a number and an amount on a piece of paper. There are rules about what details must appear on the invoice, when to apply withholding, which forms to file with the Tax Agency and by what deadlines. This guide covers everything you need to know to invoice without errors from day one.
Before issuing your first invoice, you need to be registered with the Tax Agency. The process consists of filing modelo 036 (declaración censal) with the Agencia Tributaria. Until February 2025, modelo 037, a simplified version, was also available, but it was discontinued. Now you can only use modelo 036.
One of the most important steps in the registration is choosing your IAE heading (Impuesto de Actividades Económicas). This code classifies your economic activity and, more importantly, determines whether the Tax Agency considers you a business freelancer (autónomo empresarial, IAE section 1) or a professional freelancer (sections 2 and 3). This classification is not a minor detail — it has direct consequences on how you invoice, whether you apply IRPF withholding and which tax forms you must file.
Registering with the Tax Agency is one step, but not the only one. You must also register with RETA (Régimen Especial de Trabajadores Autónomos) at the Social Security office. They are two different agencies with independent processes, and both are mandatory before you start invoicing.
This is the most important distinction you need to understand as a freelancer, and many people discover it too late. It all depends on the IAE heading you chose when registering. Business freelancers (autónomos empresariales, section 1) are those who carry out retail, hospitality, construction, manufacturing or similar activities. Professional freelancers (sections 2 and 3) are those who provide services based on their qualifications — lawyers, consultants, doctors, architects, designers, developers, etc.
The practical difference is clear: professional freelancers apply IRPF withholding when invoicing businesses or professionals, which means the client pays them 15% less (or 7% less if they are new) and pays it directly to the Tax Agency on their behalf. If more than 70% of your income as a professional is subject to withholding, you do not even have to file modelo 130. Business freelancers, on the other hand, never apply withholding, but must always file modelo 130 with a quarterly instalment payment of 20% of the profit.
Every invoice you issue as a freelancer must comply with the requirements of article 6 of RD 1619/2012. This is not a matter of aesthetics or preference — it is a legal obligation. If any mandatory detail is missing, the invoice may be considered invalid, and your customer might not be able to deduct the VAT.
The mandatory details include: a sequential number (and series if you use multiple), the date of issuance, your full name and NIF as issuer, the full name, NIF and address of the recipient, a description of the goods or services, the base imponible with the VAT rate and amount broken down, and the total amount. If you are a professional freelancer invoicing a company, you must also include IRPF withholding (7% or 15%) and subtract it from the total.
The numbering must be sequential within each series, with no gaps. If you use invoicing software, this is managed automatically. If you invoice manually or with spreadsheets, maintaining sequential numbering is your responsibility.
IRPF withholding is probably the concept that causes the most confusion among new freelancers. The first thing you need to know is that not all freelancers apply it. Only professional freelancers — those registered under IAE sections 2 and 3, such as lawyers, consultants, architects, designers or doctors — must include IRPF withholding on their invoices, and only when invoicing other businesses or professionals. When you invoice an individual (a natural person not acting as a professional), withholding is never applied.
The standard withholding rate is 15%. However, if you have just registered as a freelancer, you can apply a reduced rate of 7% during the year of registration and the following two full calendar years. The condition is that you were not registered as self-employed in the preceding year. It is a significant tax advantage during your first years of activity.
Business freelancers (autónomos empresariales, IAE section 1: retail, hospitality, construction, manufacturing) never apply IRPF withholding on their invoices. Instead, these freelancers must always file modelo 130 for quarterly instalment payments, which is a different way of advancing IRPF to the Tax Agency on a quarterly basis.
Beyond issuing invoices, being a freelancer means filing periodic returns with the Tax Agency. The most important ones are quarterly, with fixed deadlines: 20 April, 20 July, 20 October and 30 January (the last one corresponds to the fourth quarter of the previous year).
Modelo 303 is the quarterly VAT return, where you calculate the difference between the VAT you charged your customers (output VAT) and the VAT you paid to your suppliers (input VAT). If the difference is positive, you pay it. If it is negative, you offset it in future quarters or request a refund in the annual return.
Modelo 130 is the quarterly IRPF instalment payment. It is calculated as 20% of the cumulative net profit for the year. It is mandatory for business freelancers and for professional freelancers who do not have at least 70% of their income subject to withholding.
At the annual level, modelo 390 is the annual VAT summary, modelo 100 is your income tax return (where you pay tax on all your income as a natural person), and modelo 347 declares operations with third parties exceeding 3,005.06 euros per year.
CokuApp is invoicing software built for freelancers and small businesses. It complies with all Spanish tax regulations.