Our Sources: How We Keep Tax and Legal Data Current

Every result on this site rests on a rule, an index, or a market figure that came from somewhere — and that somewhere matters. A tax calculator built on guesses is worse than no calculator at all. Here's exactly what we rely on and how we keep it current.

Three kinds of source, treated differently

Official tax sources — primarily the AEAT (Agencia Tributaria)'s own published manuals, for figures like IRPF rental-income reduction rates. These are the highest-authority source for tax rules and are reviewed annually or whenever a legal change is announced.

Official legal sources — primarily the BOE (Boletín Oficial del Estado)'s consolidated text of the LAU (Ley de Arrendamientos Urbanos), for rules like deposit amounts, rent-update caps, and expense-sharing between landlord and tenant. Reviewed on legal change, not on a fixed schedule, since law doesn't change on a calendar.

Official index data — primarily INE (Instituto Nacional de Estadística) figures like the IRAV (Índice de Referencia de Arrendamientos de Vivienda) and IPC, which feed rent-update calculations. Checked monthly, since INE publishes on a monthly cadence.

Market assumptions — figures like typical insurance costs or property management fees, which aren't set by law and genuinely vary by provider. We label these explicitly as market assumptions, not legal facts, and review them more frequently since market prices move faster than law.

Every calculator shows its own sources

Look for the "Sources and last update" line on any calculator page — it names the source types behind that specific result and the date the underlying rules were last reviewed. We'd rather show you an honest "last checked" date than let a number sit silently and go stale.

Why this distinction matters in practice

A legal fact (the deposit is one month's rent for housing leases) and a market assumption (insurance typically costs 3.5-6% of annual rent) carry very different kinds of certainty. Presenting both with the same confident tone would be misleading — so we don't. When a figure is a market range rather than a fixed rule, our articles say so explicitly and point you toward getting a current quote rather than treating our number as final.

What we do when a rule changes

Tax and rental law in Spain changes — sometimes significantly, as with the 2023 housing law reforms. When a rule we rely on changes, updating the underlying figure is the priority; we don't let outdated numbers linger just because an article hasn't been revisited yet.

Quick answers

Are your numbers legal or tax advice? No. Every calculator and article on this site includes a disclaimer for exactly this reason: results are indicative estimates based on general rules and the inputs you provide, not personalized advice for your situation. Consult a qualified professional before making a decision based on any figure here.

What if I think a figure is out of date? Sources and review dates are shown on every calculator specifically so this is checkable — if something looks stale, the review date will confirm it one way or the other.

This article offers general, educational information and does not constitute tax, legal, or financial advice.