How to Check AI Answers About Property Investment in Spain

Treat an AI answer on Spanish property as a hypothesis and check it against three sources: the BOE for the rule and its version on the date you need, the tax authority's site (AEAT, and in Catalonia also ATC) for the rate and the payment procedure, and Registradores for the status of the specific property. Anything you cannot find in a primary source stays out of the calculation.

How do you check an AI answer on Spanish property in six steps?

1. Write the claim down so it can be checked. "ITP is about 10%" cannot be checked: no region, property type, buyer or date is named. "ITP on resale housing in Catalonia for a buyer who is not a gran tenedor (large property holder), from 27 June 2025" can be checked.
2. Find the act in the BOE and open the consolidated text. The page shows the date it took effect, the date of the last update and notes on amendments and repealed provisions. The BOE states that the consolidated text is informational and that the official publication has legal force.
3. Pick the version for the date of the deal. An article has a list of versions with dates, and versions that have not yet taken effect are marked separately. A rule the AI quotes could have applied in 2023 and not apply now; the reverse happens too, when the text already contains a version that will only take effect in 2027.
4. Check the regional level. ITP (transfer tax), AJD (stamp duty on documents) and ISD (inheritance and gift tax) depend on the region. The Catalan rates are published by ATC, the Madrid ones by the Comunidad de Madrid.
5. Check the tax interpretation. The filing procedure and the rates for residents and non-residents are set out in the practical guides of the AEAT, and explanations of disputed cases sit in the DGT consultation database.
6. For a property, request a document from the registry. The Colegio de Registradores issues the nota simple (registry extract) and the certificación. The registrars themselves describe the nota simple as «puramente informativa», while the certificación is signed by the registrar and carries fe (public faith). More on the document in the article on the nota simple.

Which six claims are wrong or incomplete as of 12 October 2026?

These are examples of what is easy to meet in answers, not quotations from a particular AI.

The fourth row shows that even two weeks change the picture: an act was issued, repealed and issued again under the same name. Until the new act is approved, read any of its provisions as temporary.

What are the red flags in the answer itself?

• No act number and no article, only phrases like "by law" and "it is customary in Spain".
• One rate "for all of Spain" where the tax is regional.
• No date for which the answer holds.
• A link to a blog, an agency portal or another AI answer instead of the BOE.
• No distinction between resident and non-resident, or between an individual and a company.
• A link that does not open or leads to a different act from the one named in the text.

How do you ask the question so the check goes faster?

Ask the AI to name the act, the article and the version on a specific date, to quote the wording, to list what depends on the region, and to say separately where it is unsure. An answer with a quotation is easier to check: you search for the phrase in the BOE text. If the phrase is not there, you do not believe the answer, however convincing it sounds.

What does the check not replace?

Checking against the primary source gives a fact about the rule, not a conclusion about your deal. Whether a rule applies to a specific situation is for an abogado (lawyer) to decide, and the tax consequences are for an asesor fiscal (tax adviser). This article is dated too: the facts in it were checked on 12 October 2026, and taxes and rental rules in Spain change quickly. The list of documents before a deal is in the due diligence checklist, and the tax map for a foreign buyer is on the investor taxes page.