Add activity or a new premises to your company and (if needed) register a sucursal in the Registro Mercantil

What you need

1. Be clear if it’s a new premises/activity or a sucursal. They’re not the same: 036 vs Registro.
2. Certificado digital/Cl@ve active. Without it you can’t file online.
3. Check if your objeto social covers the new activity. If not, you need notary and Registro.
4. Check last year’s cifra de negocios: if >1.000.000 €, IAE (840/848).

Documentation

• NIF and company/self-employed data.
• Poderes of the representative and their DNI/NIE.
• Modelo 036/037 with the new IAE epígrafe and premises details (address, start date, m2).
• Rental contract or proof of availability of the premises (in case of inspections or for licences).
• If sucursal: acuerdo del órgano, escritura pública and designation of representante de sucursal.
• If you modify estatutos: escritura and Modelo 600 (normally exento) for your CCAA.

Step by step

1. Pick the route: AEAT only (036) for extra activity/premises; AEAT + Registro Mercantil if it’s a sucursal or you change objeto social.
2. AEAT (036): go to sede.agenciatributaria.gob.es > Censos > 036/037. Mark modificación, add the epígrafe IAE and the new premises in “Lugares de realización de la actividad”. Sign and submit. Download the acuse.
3. IAE (if applicable): at sede.agenciatributaria.gob.es > Tributos > IAE, file Modelo 840 for alta and 848 if there’s a quota variation. If you’re exempt, don’t file the 840.
4. Objeto social missing activity: go to notary to modify estatutos. Then file Modelo 600 and submit the escritura to the Registro Mercantil electronically.
5. Sucursal: execute the escritura de apertura and appoint the representative. File at sede.registradores.org/site/mercantil, pay aranceles and wait for inscripción and BORME.
6. Keep everything: 036 receipt, IAE documents (if any), RM inscription/BORME. Update invoices and website with the new premises.

Expert tips

• Don’t confuse local with sucursal: 90% of rejections come from trying to register basic openings as sucursales.
• In the 036, fill in “Lugares de realización” properly. If you leave it blank, you’ll get a requerimiento.
• If you’re unsure about the IAE epígrafe, check the IAE tables and pick the most specific one; changing later means another 036.
• The sede de Registradores works better on a desktop with the certificate installed. Avoid mobile if you don’t want to suffer.

Common mistakes

1. Filing the 036 late. Result: 200 € fine for a censal obligation, over something avoidable.
2. Opening a sucursal without escritura. The Registro will reject it and you’ll lose weeks.
3. Forgetting IAE when you exceed 1M. Later comes recargos and it’s a hassle.
4. Outdated objeto social. Banks and public tenders can block you if activities don’t match.
5. Thinking the ayuntamiento is irrelevant: to open to the public you’ll need a licencia or declaración responsable separately (another trámite).