IMI calculator

This is the most common confusion, and an expensive one: the demand that lands in May is not the tax for the year in which it arrives. IMI relates to the year in which the property stands on the register at 31 December, is assessed by the tax authority between February and April of the following year, and is paid in May, August and November of that following year. The demand arriving in 2026 is therefore the 2025 IMI, worked out with the rates municipalities set for 2025.

That is why this calculator does not ask you for a year. It always uses the most recent year the tax authority has published, and tells you which one, because a given year's table only appears on the Portal das Finanças around assessment time. If you come here one day and the page says the current year's rates are not out yet, that is the reason.

The tax falls on the rateable value, which is the figure on the caderneta predial — not the market value, nor what you paid. On older properties carrying a dated assessment the gap between the two can be substantial, and it is always the register figure that counts.

The rate for urban property moves within a statutory range running from 0.3% to 0.45%. The same house, at the same rateable value, pays different amounts depending on the municipality — and eight municipalities go further and set the rate parish by parish, under article 112.º, n.º 5, of the IMI Code. For those, the calculator also asks for the parish, because without it there is no rate to apply.

Left out of the calculation are the increases and reductions some municipalities apply to derelict or vacant property, or to urban regeneration areas. They are decided case by case and appear in no public table that can be read municipality by municipality.

Households with dependants can have the IMI on their own permanent home reduced by 30 € with one dependant, 70 € with two and 140 € with three or more. The amounts are fixed in law and do not vary; what varies is adoption, because each municipality decides whether to apply it.

The deduction reaches only the property where your tax residence is registered, it counts the household as it stood on the last day of the previous year, and the tax authority applies it automatically from the register and your income return — there is nothing to claim. Switch the option on in the calculator and it will tell you whether your municipality adopted it.

The surcharge does not look at each property on its own: it adds up the rateable values of every urban property the holder owns at 1 January and taxes the total. An allowance of 600 000 € is deducted, doubling where a married couple or civil partners opt for joint taxation, and above that the charge is progressive for individuals.

A detail almost every second-hand account gets wrong: the one and two million thresholds are measured against the sum of rateable values before the allowance, not after. Another: the progressive bands belong to individuals and to them alone. An undivided estate has the same allowance and the same base rate, but pays that rate on everything above the allowance, with no bands. A company pays 0.4% from the first euro, with no allowance at all.

Property classified as retail, industrial or for services is outside the surcharge, as is property classified as other. And the calendar is different: AIMI is assessed in June and paid in September of the very year it relates to, unlike IMI, which is paid the following year. When the calculator shows the two added together, it is adding what leaves your account within the same calendar year — and it tells you, month by month, when it leaves.