Register an additional dwelling in Catastro for your property

What you need to have handy

1. Cl@ve or certificado digital to access the Sede del Catastro.
2. Referencia catastral of the original property (on the IBI or in the Sede).
3. Licencia/comunicación previa and fecha de fin de obra.
4. Certificado final de obra or a technical document with superficies.
5. Escritura de obra nueva/división horizontal if there are two independent dwellings.
6. Planos acotados (plans, superficies construidas and útiles, usos).
7. DNI/NIE of the owner and, if applicable, a signed autorización from the represented party.
8. Recibo del IBI from the last year and, if you have it, GML of the building.

Documentation

• Identity: DNI/NIE del titular. Representation paperwork if you're not the owner.
• Title and works: licencia/comunicación previa and the certificado final de obra.
• Property: escritura de obra nueva y división horizontal (if it exists), with description and cuotas.
• Technical: planos acotados showing superficies by rooms/floors; preferably signed by a técnico.
• Property data: referencia catastral and recibo del IBI.
• Optional but useful: GML file with georreferenciación of the building and clear photos.

Step by step

1. Check the deadline: you have 2 meses from fin de obra/escritura. Don't leave it to the last day.
2. Log in at https://www.sedecatastro.gob.es with Cl@ve. Go to Trámites > Declaraciones and open Modelo 900D (alteraciones de inmuebles urbanos).
3. Fill it in: your details, referencia catastral, mark alta de nueva vivienda por división/segregación, indicate uso (residential), superficies and año. Don't mix useful (útil) with constructed (construida).
4. Attach PDFs: the licencia, certificado final, escritura (if there's división horizontal), planos and any required docs. If you have GML, upload it.
5. Submit and download the justificante with the expediente number. Watch your notifications; they may request subsanación.
6. In person alternative: if the Sede trolls you or you don't have Cl@ve, book a cita at the Gerencia from the Sede and file the Modelo 900D on paper with copies of everything.
7. Follow up: check the status with the expediente number. When it's processed, verify in Consulta descriptiva y gráfica that the new dwelling and its referencia appear.

Tricks that save you time

• Ask the notario to send the escritura to Catastro if there's división horizontal. Sometimes that avoids the 900D.
• Combine the planos and the certificado into a single clear PDF. Fewer attachments, fewer problems.
• Name files ("licencia.pdf", "final_obra.pdf", "planos.pdf"). Sounds trivial, but it helps if they request more info.
• If the site errors, try Chrome and keep PDFs <10 MB.
• If there are multiple co-owners, include/attach written autorización from the others or an agreement act.

Typical mistakes that can derail the procedure

1. Expecting a new referencia without división horizontal: Catastro may record it as a reforma only.
2. Mixing superficie útil with construida: your square metres won't match and you'll get a requerimiento.
3. Entering the wrong referencia catastral: expediente goes to the bin and you start over.
4. Not responding to a requerimiento on time: the expediente can be archived and you lose time.
5. Thinking Registro and Catastro sync automatically: they don't always. File yourself and confirm it's published.
6. Leaving the 2 meses deadline to the last minute: being late exposes you to sanciones and IBI recargos.