The empty house: how IMI triples after a year

Roughly 40 to 50% of dwellings in Algarve coastal municipalities are secondary or seasonal homes. The state treats a house that produces nothing for a year as a problem, and prices it accordingly. Here is the rule, the numbers, and the routine I use on my own units.

What "devoluto" means in law

A property is classed as empty (prédio devoluto) when, for a year, it shows no sign of use: no water, electricity or gas contract, or annual consumption below 7 cubic metres of water and 35 kWh of electricity, or no evidence of occupation. The council classifies after notifying the owner at the address on the tax record. Legal basis: Decree-Law 159/2006 as amended, which also sets the consumption thresholds.

Two things owners get wrong:

• The letter goes to the registered address. For many foreign owners that is the empty house itself.
• The year is counted from the readings, not from your last visit. Thirteen days in August do not reset it if the rest of the year reads zero.

What it costs

Once classed, the IMI rate is tripled. In a municipality that has declared an urban pressure zone the rate is multiplied by 10, rises 20% each following year the property stays empty, and is capped at 20 times the normal rate (Municipal Property Tax Code, article 112-B).

Run your own numbers in the empty house IMI check.

Pressure zones are declared by each municipality. Few Algarve councils had done so at the time of writing, but Lisbon and Porto have, and the list changes. Ask before assuming.

The other costs of an empty house

The IMI increase is the only one with a formula. The others are bigger and arrive without a letter:

• Water. A burst flexible hose under a sink runs for months. In my experience it is the most common insurance claim in closed apartments, and insurers reject it when the property was unoccupied beyond the period in the policy, often 30 or 60 days.
• Damp and mould. Closed shutters from October to May in a coastal climate. Repainting a two-bedroom after one winter of mould: €1,500 to €3,000.
• Occupation. A visibly empty house is a target. See squatters: what the 2025 law changed.
• Condomínio votes. Decisions taken at meetings you do not attend, including works you pay for.

What to do if you receive the notification

1. Reply within the deadline on the letter (usually 10 to 30 days) with proof of use: bills, a lease, a licence for works, or dated photos.
2. If the classification stands, start regular use or let the property; the increased rate stops from the following year.
3. If you plan to sell, remember that a devoluto classification is public information a buyer's lawyer will find.

The short version

Keep both meters above the thresholds, keep the proof, and make sure someone receives post at the property. A monthly visit does all three. It is the base of my property management service, and the first thing I check in the free yield audit.

Sources: Decree-Law 159/2006 (definition and thresholds); Municipal Property Tax Code article 112-B (rate increases); municipal pressure-zone declarations. Last checked 2026-10-10. Rates change; confirm with your accountant or lawyer before acting.