Declare an additional dwelling in Catastro (new unit in your property)

What you need to have to hand

1. Cl@ve, certificado digital or DNIe that works in your browser. You can’t sign online without it.
2. Referencia catastral of the original property (la finca matriz). You’ll find it on the IBI receipt or on the Sede.
3. Date of end of works or of the escritura that gives rise to the new dwelling.
4. Areas: constructed and useful area of the dwelling and of any anejos (if any).

Documentation

1. DNI/NIE of the holder and of any co-holders.
2. Escritura de obra nueva and/or división horizontal (if it exists), preferably with the nota de inscripción.
3. Building licence and licencia de primera ocupación or equivalent declaración responsable.
4. Certificado final de obra from the competent technician.
5. Plans with floor layout and surfaces and memoria técnica. They must be legible and signed.
6. IBI receipt of the original property (to identify referencia and ownership).
7. Representation: notarial power or apoderamiento if a third party files it.

Step by step

1. Go to sedecatastro.gob.es > Trámites > Declaraciones y comunicaciones and identify yourself with Cl@ve/certificado.
2. Open the declaración por variación física (modelo 900D) and enter the referencia catastral of the original property.
3. Fill in details: holders, date of end of works/escritura, uso Residencial, areas and anejos. If there’s a división horizontal, state the elemento privativo and cuota.
4. Attach PDFs: escritura (if applicable), licences, certificado final de obra, plans and memoria. Check that the metres match across documents.
5. Sign and submit. Download the justificante with CSV and save the expediente number.
6. In Mis Expedientes, watch for any requerimiento de subsanación. If they ask for something, upload it using “Aportar documentación a un expediente” within the deadline.
7. If you can’t do it online, book a cita at your Gerencia del Catastro from the Sede and submit the modelo 900D on paper with copies and originals for checking.

Time-saving tips

1. Check areas beforehand: if escritura, plans and licence don’t match, they’ll return it.
2. Compress PDFs and use black & white; the Sede limits size and rejects some formats.
3. If there are multiple holders, add an extra page with the ownership split or upload them in a single clear PDF.
4. Turn on electronic notifications (DEHú) so you know as soon as there’s movement.
5. If it’s due to división horizontal, ask the notary/registrar for digital simple copies; they display better and weigh less.

Common mistakes that will mess up your application

1. Submitting without final work certificate: they’ll stop the file until you provide it.
2. Not declaring anejos (trastero/garage): later the IBI won’t match and you’ll get requests.
3. Uploading loose photos instead of an ordered PDF: the technician can’t decipher them and will ask for more.
4. Inconsistent dates between licence, end of works and escritura: that raises flags and delays processing.
5. Going to the Gerencia without a cita: they’ll send you home. Book it well in advance — they fill fast.