Autónomo status in Spain is not a single stamp. You affiliate as a self-employed worker in the Régimen Especial de Trabajadores Autónomos (RETA) with the Tesorería General de la Seguridad Social (TGSS), and you declare the activity in Agencia Tributaria's census of entrepreneurs, professionals, and withholders. Older guides still mention modelos 036 and 037 together; AEAT withdrew the simplified 037 route, so new census altas run through modelo 036. Get your NIE, electronic access, and a Spanish IBAN ready before either filing.
Which order should you follow?
Complete both altas on or before the day your activity starts, with the same start date. Late filing can cost incentives and trigger surcharge rules. A practical sequence many foreigners use is: confirm you already have a Social Security number if Spain never assigned one, open or confirm a euro account for cuota collection (open a bank account), set electronic identification, then file RETA alta in Importass and the Hacienda census alta in close succession.
Importass "Alta en trabajo autónomo" asks for activity codes, expected net earnings, contribution base, mutual insurance choice, contact data, and IBAN. TGSS also needs the Impuesto sobre Actividades Económicas (IAE) epígrafe that matches the business you will invoice. Pick the epígrafe from the official IAE tables for the work you actually sell, not a vague label.
Hacienda modelo 036 is the census declaration that registers start of activity, tax obligations (including VAT and personal income tax options where they apply), and related census data. Foral territories use their own Hacienda channels when you are under those rules. A digital certificate or Cl@ve makes both portals usable without endless in-person queues.
What about Tarifa Plana and later taxes?
Tarifa Plana is a time-limited starter scheme for eligible new RETA afiliados. Duration, eligibility gaps after a previous alta, and any extension if forecast earnings stay below the national minimum wage reference are set in Social Security rules and change over budget cycles. Do not rely on a blog's exact monthly cuota. Check the live amount, MEI add-ons, and eligibility inside Importass or TGSS pages when you file.
After alta, you still have ongoing tax filings: quarterly and annual calendars depend on the options you marked in the census. See filing taxes in Spain for the return side. Autónomo alta also sits beside the wider paperwork after moving chain; immigration status and RETA affiliation remain separate decisions.
Common misconceptions
One misconception is that obtaining a NUSS alone registers you as autónomo. The number identifies you; RETA alta creates the self-employment affiliation.
Another is that you can invent any IAE epígrafe because "Hacienda will fix it later." Wrong codes create wrong VAT and withholding expectations from day one.
It is also wrong to publish an evergreen exact Tarifa Plana figure as if it never changes. Treat it as a time-limited benefit and verify the current TGSS amount before you budget.
Summary
Align RETA alta and Hacienda modelo 036 on the same activity start date, with NIE, electronic ID, IBAN, and a truthful IAE epígrafe. Use Importass for Social Security and AEAT for the census. Check Tarifa Plana live on TGSS tools, then keep tax calendars and immigration documents on separate tracks.
Sources
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