Can I invoice in Spain without being registered as autónomo?

Tax registration, RETA and invoices: three separate checks

This guide concerns work you carry out on your own account as a business or professional activity in Spain. It does not cover a salary, a gift or an occasional sale of your personal belongings. Before assuming that “one invoice will be fine”, separate these obligations:

Tax registration is due before the activity or operations begin, not when the first payment arrives. Article 9.4 of the census regulations also covers purchases, payments and hiring staff for that activity. Your actual start date may therefore precede your first invoice.

Source: Spanish Tax Agency: when to register. Read alongside article 9.4 of RD 1065/2007. Checked 26 September 2026; source in Spanish.

Earning below the minimum wage is not an automatic RETA exemption

RETA is Spain’s Social Security scheme for self-employed workers. Registration is required when the activity meets its conditions, including habituality. The official Importass guidance expressly says that personal, habitual activity requires registration regardless of the income it generates. There is no general permitted number of invoices or monthly amount that authorises working without contributions.

Source: Importass: registering as self-employed. Legal basis: article 305.1 of Spain’s General Social Security Law. Checked 26 September 2026; source in Spanish.

In judgment 162/2026 of 16 February, Spain’s Supreme Court confirmed that income below the Spanish statutory minimum wage, the SMI, does not by itself rule out habitual activity. Comparison with the SMI can be an indication, but its significance depends on the activity and the other circumstances. “I earn very little” is not permission to remain unregistered.

A genuinely isolated assignment requires an assessment of whether the activity is habitual. Neither its price nor a single invoice settles that question: one invoice may cover several months of ongoing work. Calling something a “side job” does not explain how regularly you do it, how you offer it or whether it repeats.

Source: Supreme Court judgment 162/2026, ECLI:ES:TS:2026:641. Legal reasoning sections four and five, pages 14 and 15 of the Spanish original. Checked 26 September 2026.

Further reading in Spanish: when autónomo registration is mandatory. This guide covers the general test and relevant circumstances.

Three situations that need different assessments

These fictional examples help you prepare for advice. They are not decisions on an individual’s legal position:

Gather work dates, contracts or assignment emails, expected and received amounts, other clients and assignments that year, expenses and equipment used. Explain whether you advertise the service continuously and whether you have a job, pension or benefit. These facts help assess your case; they are not a checklist that guarantees an exemption after ticking a few boxes.

What to do before issuing the invoice

1. Identify what you supply and when the activity began. Check whether it is own-account economic activity and which tax authority is responsible.
2. Notify the relevant tax registration and obligations before starting. Do not use the payment date automatically as the start date.
3. Determine your Social Security position. If RETA applies, Importass requires registration before you begin; registering after starting is late registration.
4. Establish the VAT treatment, any exemption and withholding based on the activity, transaction and customer. Do not copy 21% VAT or 15% withholding from someone else’s invoice.
5. Issue and retain the invoice, record the income and identify the returns and payments due, including after the assignment ends.

A full invoice must include, among other particulars, its number and series where applicable, issue date, supplier and customer identification and addresses, the required tax identifiers, a description, taxable amount and applicable VAT rate and amount. If the transaction date differs from the issue date, include it too. Exempt transactions and other special cases have additional rules.

Source: Spanish invoicing regulations: article 6. Requirements for a full invoice differ from those for a simplified invoice.

Withholding does not arise simply because your customer is a company. The income must be subject to withholding and the payer must be required to withhold. It may apply to professional services; an ordinary business sale is not automatically treated the same way. Withholding neither replaces registration nor represents the professional’s final income-tax bill.

Source: Spanish income-tax regulations: articles 75, 76 and 95. Income subject to withholding, parties required to withhold and rates for economic activities.

Example: the amount collected does not decide registration

Assume a professional service supplied to a Spanish company, located for VAT purposes in mainland Spain or the Balearic Islands. The standard 21% VAT and 15% professional withholding rates have been found to apply: no exemption, different VAT rate or reduced withholding is available in this example. For a €500 fee:

• Fee before tax: €500.
• VAT: €500 × 21% = €105.
• Withholding: €500 × 15% = €75.
• Customer payment: €500 + €105 − €75 = €530.

The €530 collected is not your profit or proof that the activity is non-habitual. VAT and withholding each have their own treatment; the fee is €500 before relevant expenses. This calculation illustrates a transaction whose tax treatment has already been established. It does not authorise issuing an invoice without the necessary registrations.

Keeping the invoice for your annual return is not enough

VAT returns, income-tax payments on account and other obligations may apply depending on your registration and activity. Check which returns are due even if the work ends before the quarter does. Annual Spanish income-tax filing has separate rules: anyone registered in RETA at any point during the tax year must file. Outside that situation, do not turn “any income” into a universal annual filing rule.

Source: Spanish Income Tax Law: article 96. The tax treatment of income and the obligation to file a return are separate questions.

If you have already worked or been paid without the required registration

Gather the actual dates of the assignment, work, invoice and payment, supporting records and any notices from the Tax Agency or Social Security. Review tax registration, outstanding returns and RETA separately. Registering today does not automatically erase an earlier period that should have been covered.

Do not alter dates to make past work appear to follow a later registration. Tax failures may lead to surcharges or penalties depending on the obligation and whether the authority had already contacted you. Voluntary correction is not treated identically in every situation. If RETA was required, back contributions, surcharges and penalties may also arise. A single fine quoted without those facts would be misleading.

Tax source: Spanish General Tax Law: articles 27, 191 and 198. Late-filing surcharges and different infringements are not a single automatically cumulative penalty.

To organise registration from the start, use the guide to becoming autónomo in Spain. When seeking professional advice, prepare the records above so you can explain the actual work, not just the amount you want to invoice.

Finlai publishes this guide. Its plans and services advertise autónomo registration and a tax adviser. Check the scope for your circumstances: buying software or advice does not create a RETA exception. Finlai does not serve the Basque Country or Navarra.