Alta e inscripción de una empresa adicional (Registro Mercantil + AEAT)

What you need to have to hand

1. Cl@ve or certificado digital (preferably the administrator’s or the representative’s).
2. Certificación negativa de denominación social from the Registro Mercantil Central.
3. Estatutos and the escritura de constitución (the notary will give an electronic copy).
4. DNI/NIE of the administrator and, if a third party acts, the poderes.
5. Bank account and the receipt of the capital social deposit (if applicable; the notary usually attaches it).

Documentation

1. Certificación negativa de denominación (RMC).
2. Escritura de constitución y estatutos signed.
3. Justificante de tasas/aranceles of the Registro and BORME announcement.
4. Modelo 036 for the alta censal (AEAT), first for NIF provisional and later for NIF definitivo.
5. Hoja registral or literal certification of inscription (for the definitivo).
6. Modelo 840/848 for IAE if you are not exempt.

Step by step

1. Reserve the name: go to https://www.rmc.es and request the certificación negativa. No name, no notary appointment.
2. Sign at the notary: bring the name and statutes. The notary usually sends electronically to the Registro Mercantil. If not, they’ll give you the copy to file yourself.
3. Register at the RM: submit via https://sede.registradores.org/site/mercantil or by appointment at your RM. Pay aranceles and the BORME. If there are defects, fix them fast.
4. Request provisional NIF at AEAT: at https://sede.agenciatributaria.gob.es, file Modelo 036 (alta) and attach the escritura. It will let you open a bank account and do first steps.
5. When registered, switch to NIF definitivo: file another Modelo 036 attaching the hoja registral. Mark obligations: IVA, retentions, epígrafes IAE.
6. IAE if applicable: if you are not exempt, file Modelo 840 and keep the receipt. If you’re exempt, don’t file forms that don’t apply.

Time-savers

1. Let the notary file to the RM: you avoid trips and formatting rejections.
2. Upload readable, signed PDFs: AEAT rejects blurry or unsigned attachments.
3. Fill the 036 calmly: wrong epígrafes or obligations means another modification 036.
4. Have Autofirma ready: signing on AEAT/Registradores portals works better with Autofirma and desktop browsers. Avoid mobiles.
5. Plan the RM appointment: some registros have full calendars. If you go on paper, book cita and bring payment proof.

Common mistakes to avoid

1. Trying for NIF definitivo without inscripción: AEAT will stop it. Wait for the hoja registral.
2. Not reserving the name in time: it expires and you get stuck on signing day.
3. Forgetting the BORME: without the announcement they won’t close the inscription and won’t issue certification.
4. Registering IAE when you don’t need to: you waste time and may generate unwanted bills.
5. Uploading documents with mismatched data (social address, different CNAE between escritura and 036): triggers requerimientos and wastes weeks.