The TA.0521 is the Social Security form that puts you on the RETA register, the special regime for self-employed workers. Without it, you are not enrolled. Tax Agency registration alone does not count, and Hacienda will eventually flag the gap. This guide walks the full filing flow on Import@ss, step by step, with the prerequisites, the field-by-field detail, the deadlines that protect your tarifa plana, and the five mistakes that cost first-year autónomos money.
The standard route is online via the Import@ss portal at sede.seg-social.gob.es. In-person is possible but slow.
Read how to register as a freelancer for the full registration journey if you have not started yet.
You will need:
If any of these are missing, the TA.0521 either bounces or registers you incorrectly.
The legal window is up to 60 days before your declared activity start date and never after. The start date you put on TA.0521 must equal or be later than the date on Modelo 036 or 037. Mismatched dates trigger a Seguridad Social review and frequently kill the tarifa plana.
If you file even one day late:
This is the single most expensive paperwork error for new autónomos.
If you have never been employed or self-employed under the Spanish system, you do not have a NAF. Request it through Import@ss using Modelo TA.1. The portal accepts digital certificate, Cl@ve, or video identification. Allow up to two working days for confirmation. Without a NAF, the TA.0521 will not submit.
If you have ever held any Spanish payroll job, you have a NAF on record. Find it on a previous nómina, or request it as a duplicate via the same portal.
File Modelo 036 (or the simplified 037 if you qualify) before TA.0521. Hacienda needs:
The date you declare here is the date that must appear on TA.0521. Misalignment is the most common rejection reason.
Go to import@ss (portal.seg-social.gob.es/importass) and identify yourself with one of:
In the personal area, choose "Alta en trabajo autónomo". The system pre-fills your NAF, NIE, and address from the Seg Social database. Verify everything before continuing.
Personal data carries over from your Seg Social profile. Update phone, email, and notification address if any are wrong.
Activity section:
Contribution and mutual:
Bank details:
Notification address:
The base sets your monthly cuota and the size of every future benefit (sick leave, maternity, pension). Higher base means higher cuota and higher cover.
In year one, tarifa plana applies regardless of base: €80 a month, around €88 with the 0.9% MEI for 2026. The base you pick still matters because it sets the calculation for sick-leave benefits if you need them in months 1 to 12.
From month 13, your cuota tracks the by-tramo table (€200 to €590, plus MEI). You can extend the €80 rate into year two if your net rendimientos stay below the 2026 SMI of €1,184 a month. See autónomo costs breakdown for the full schedule and autónomo taxes 2026 for how the cuota interacts with IRPF.
For the mutual, the practical advice: pick whichever has a clinic close to where you live. They handle sick leave certificates and you will not want to drive an hour for one.
Submit the form. Import@ss returns a Resolución de alta with a digital reference number. Save the PDF. This is your proof of RETA enrolment.
The first cuota is direct-debited on the last day of the next full month. If you registered on 15 February with a 1 March start date, the first €88 is debited on 31 March.
Two checks to run within 7 days:
If either is missing, call Seguridad Social at 901 50 20 50 with your Resolución reference.
The TA.0521 has a few variants for non-standard self-employed profiles:
Structure is similar but the contribution rules differ. Autónomo societario, in particular, has its own minimum cuota base that overrides the standard tramo table.
Tarifa plana eligibility (€80 base for 12 months) is conditional on a clean alta:
Any of these missing and you drop to the by-tramo schedule from day one. The difference is roughly €1,400 across the first year on a low-band autónomo. File correctly and the saving stays.
Can I file TA.0521 the same day I start working? Legally yes, but in practice no. Filings take a few hours to process and any next-day clearance puts your alta date one day after your declared start. Always file at least one working day in advance.
Do I need a digital certificate to file TA.0521? No. Cl@ve PIN works, and so does SMS verification if your Spanish phone number is registered with Seguridad Social. A digital certificate is the most reliable option but not the only one.
What happens if I file Modelo 036 but never file TA.0521? Hacienda treats you as registered for tax purposes. Seguridad Social does not. You start accumulating undeclared activity, and when discovered (often during a cross-check), you owe back cuotas plus surcharges, and the tarifa plana is gone.
Can a foreigner without NIE file TA.0521? No. The NIE is mandatory. Foreign EU citizens use the NIE issued at registration; non-EU residents need a residence permit that authorises self-employment first.
How long does the alta take to confirm? Usually within 24 hours when filed online. Allow 3 to 5 working days during peak periods (start of January, post-summer).
If you would rather skip the paperwork, renn handles autónomo registration online end to end, including TA.0521.
