Due diligence before buying: the checks that avoid nasty surprises

By Ignacio Capote Cánovas - Octubre 2026

Most problems in a purchase are avoided with good prior checks. Buying on the trust of the agency or the seller is the most expensive mistake we see. A week of work done well can save you years of grief.

What we check before you sign. The Land Registry extract, to know the true owner and whether there are mortgages, charges or easements. The planning status and licences, including the first-occupation licence, to rule out illegal or non-conforming works. The community of owners' certificate, because community debts attach to the property itself. That the IBI is up to date. The energy certificate and the building's condition. And that the Registry description matches the Cadastre and physical reality.

For new builds, additionally. We check the guarantee or insurance of the sums paid on account, and the developer's warranties.

And the seller. We verify their identity, their capacity, their marital status and matrimonial property regime, and the validity of the power of attorney if a representative signs.

Legal analysis. Two rules explain why this matters. Article 1483 of the Civil Code protects the buyer against undeclared hidden charges, but claiming afterwards is slow; the real protection is the prior check. And article 9.1.e) of the Horizontal Property Act establishes that the property is charged with the community debts of the current year and the previous three: if you don't check, you can inherit someone else's debts. That's why a buyer's lawyer, independent of the agency and the seller, is not an expense — it's the insurance on the transaction.