Before selling in Spain: why your property should match the Catastro, the Registro and reality

I see this scene almost every week in my office. Someone wants to sell their home on the Costa Blanca, a buyer comes along, everything is going well… and suddenly the deal stalls because the property "on paper" is not the same as the property in reality. There is a pool that does not appear anywhere, a covered porch that was turned into a bedroom, a few extra square metres. And that, which seems like a minor detail, can put a sale at risk.

In many cases, the situation can be regularised before the property goes on the market. I will explain it step by step, without technical jargon.

What does "declaring a new build" mean?

Declaring a new build simply means formally recording that a construction exists on a plot of land. When the land was purchased or inherited, the paperwork may have shown only bare land, or a smaller house. If something was then built or extended, that change needs to be reflected. Until it is, the real property and the registered property do not match.

Think of your property as having three "photographs" that should all be identical: physical reality (what is actually built), the Registro de la Propiedad (who owns it and what encumbrances it carries) and the Catastro (what appears in the cadastral register for tax purposes). When all three photographs align, selling is straightforward. When they do not, the problems begin.

The Catastro and the Registro are not the same thing (and they do not always coincide)

Many people confuse them, so let us separate them clearly. The Catastro is an administrative register kept for tax purposes and describes the property physically: floor area, use, location. It is what determines, for example, your IBI (annual property tax) bill. The Registro de la Propiedad, by contrast, records who the owner is and what encumbrances exist on the property (mortgages, charges, easements).

For years they operated independently and it was normal for them to diverge. Since Ley 13/2015 both are required to coordinate: when the graphic description of a property is registered, the Registro and the Catastro agree on its boundaries and floor area. That is why today, before selling, it is worth checking that both photographs say the same thing as reality.

Two routes: completed build and build "by age" (por antigüedad)

Not all builds are declared in the same way. The law (the Consolidated Land Act, known as TRLS, in its article 28) provides for two routes, and knowing which one applies to you makes a significant difference to the process.

1. Completed new build (with a licence)

This is the standard route when the construction was carried out with a municipal building licence and a final completion certificate. It is declared before a notary by submitting that technical documentation and is then registered at the Registro. This is the straightforward route: there are documents proving that everything was done in accordance with the rules.

2. New build on grounds of age (art. 28.4 TRLS)

This is the most common situation with older coastal properties. Here the construction or extension has no licence, but so much time has passed that the authorities can no longer require it to be demolished. When this occurs, the law allows registration by submitting a technical certificate (from an architect or building surveyor — arquitecto técnico), a catastral certification or a notarial deed proving that the build was completed by a specific date.

A crucial distinction: registering a build by age is NOT the same as "legalising" it for planning purposes. These are different things. Registration allows you to sell, mortgage or inherit the property normally; the planning status of the construction remains as it is. That is why it is important to have your specific case reviewed before assuming anything.

Why this can block a sale (or complicate an inheritance)

When the square metres do not add up, the problems appear at a late stage, once a buyer is involved. Here is what typically happens:

• The buyer's bank values the property and finds that the actual floor area does not match the Registro: it either reduces the mortgage or refuses to grant it.
• The buyer, quite reasonably, loses confidence and walks away, or demands a price reduction.
• The home insurance policy may not cover the part of the property that is not declared.
• In an inheritance, as a general rule the property can be registered in the heir's name with the description already recorded at the Registro, but the unregistered construction will stay off the record until the new build is declared.

Much of this can be avoided with advance planning.

How much does it cost and how long does it take

Let me give you a general guide, because every case is different. Several professionals and bodies are involved in regularisation, each with their own costs: the technical expert who signs the certificate (architect or building surveyor — arquitecto técnico), the notary, the Registro de la Propiedad, the tax on the deed (Actos Jurídicos Documentados, a form of stamp duty) and the update at the Catastro.

In terms of time, once the technical documentation is ready, the process generally moves within a range of a few weeks to a couple of months, depending on the workload at the Registro and the Catastro. What takes longest, almost always, is getting the technical side properly prepared. That is why I insist: starting early is advisable.

How to regularise the Catastro–Registro–reality chain

This is the logical order I follow when I handle a case like this:

1. Identify the discrepancy: I request an up-to-date nota simple (property extract) from the Registro and compare it with the catastral reference and the actual property.
2. Commission the technical certificate: an architect or building surveyor (arquitecto técnico) certifies the description of the build and, if the age route applies, its completion date.
3. Choose the correct registration route: for small discrepancies, registering the graphic representation (art. 199 of the Ley Hipotecaria) is usually sufficient; for large discrepancies, a specific notarial procedure may be required (art. 201). Choosing the right route helps avoid rejection by the registry.
4. Execute the new-build declaration deed (completed or by age) before a notary, with the technical documentation.
5. Register at the Registro de la Propiedad and confirm that the registered description now matches reality.
6. Update the Catastro so that the floor area and use are aligned, ensuring the problem does not resurface in the next transaction.

Checklist before putting up the for-sale sign

If you are thinking of selling — or inheriting — a property in Spain and are not sure whether your paperwork is in order, you are welcome to contact me. That is how I work: first understand your case, then prevent, and only then act.