Key figures — as of 2026-08-20: VPT (taxable property value) can be revalued free of charge every three years via Modelo 1 on Portal das Finanças, deadline 31 December — new value applies to the following year's IMI — Government construction-value coefficient used in VPT calculations rose to €712.50/m² in 2026, up 7.1% from €665 in 2025 — municipal IMI rates remain 0.3%–0.45% for urban property (0.8% rustic) — the increase applies automatically only to new, modified, reconstructed or freshly reassessed properties, not to VPTs already fixed.
Why this matters now
Most foreign owners in Portugal know their IMI bill arrives every spring, calculated on the property's Valor Patrimonial Tributário (VPT) rather than the price they paid. What fewer realise is that this VPT isn't frozen. Property owners can request a fresh valuation every three years, free of charge, provided no changes have been made to the property since the last assessment. That three-year clock is now catching up with a wave of properties bought or last assessed around 2022–2023, and for some it will land alongside a less visible mechanism: the periodic inflation-linked adjustment the Autoridade Tributária applies to VPTs in between full reassessments.
The mechanics: two updates, not one
Portugal actually runs two separate VPT update processes, and conflating them is where owners get caught out. The first is the one most people know: every three years any owner can ask Finanças for a new VPT assessment, free of charge, by submitting Modelo 1 of the IMI declaration on Portal das Finanças by 31 December each year, with the new value only taking effect on the following year's IMI. This request recalculates the property using current coefficients — location, quality, age — and can lower the tax as easily as raise it, particularly for older homes whose coeficiente de vetustez was never updated.
The second is quieter and automatic. In periodic updates, instead of recalculating all the usual parameters, the AT applies 75% of the currency devaluation coefficient to the originally assessed VPT, with the explicit purpose of adjusting the value to inflation — which always results in an increase to VPT and, consequently, IMI. Owners don't apply for this one and can't opt out of it; it simply happens.
Layered on top of both is a separate 2026 change to the construction-cost input used whenever a property is newly assessed. The average construction value per square metre used in VPT calculations rose to €712.50 in 2026 — up 7.1% on the figure that applied between 2023 and 2025 — under Portaria 471/2025/1. Crucially, this increase affects only new, modified, reconstructed or freshly reassessed properties — it does not automatically apply to properties already assessed under the old rate. In other words, if your villa or apartment happens to fall due for its three-year revaluation this year, it gets measured against a noticeably higher construction benchmark than a neighbour whose property isn't due for reassessment until 2027 or 2028.
What it means in euros
Municipal IMI rates themselves haven't moved — urban property rates still sit between 0.3% and 0.45%, set by each municipality within that range — so the increase runs entirely through the VPT base, not the rate. GrowIN's own reading of the formula shows why that still matters: because the construction-value coefficient multiplies directly into the VPT calculation, a straight 7.1% rise in that input produces roughly the same percentage rise in VPT for any property reassessed this year, before location or quality coefficients are even considered. On a mid-sized 150m² home with an average location multiplier, that works out to a VPT increase in the region of €7,000–€8,000 — translating to perhaps an extra €25–€35 a year in IMI at a typical 0.35% municipal rate. Modest on its own, but it compounds with every future three-year cycle, and it says nothing about what a full reavaliação might also reveal if the location coefficient for a gentrifying Algarve or Porto neighbourhood has moved too.
The practical takeaway
Foreign owners should check the caderneta predial on Portal das Finanças to see when their property was last assessed. If it's been three years or more, a revaluation could go either way — running a simulation before submitting Modelo 1 is the sensible move, since the same request that might lower an outdated age coefficient could also expose the property to the new, higher construction-value benchmark. As GrowIN Portugal Editorial puts it: the three-year clock on your property's tax value doesn't ring an alarm — it just adds euros to your bill.
Owners with larger portfolios should also keep an eye on how VPT increases interact with the AIMI wealth surcharge, which applies above certain aggregate thresholds. For a fuller breakdown of ownership costs, see our tax & NIF guide to property taxes in Portugal.
What to watch next
Municipalities set their annual IMI rate by year-end, so any rate changes for 2027 will emerge around December. Owners due for their three-year window in 2026 have until 31 December to file Modelo 1 if a revaluation looks favourable — but with the construction-value benchmark now higher, it's worth running the numbers with an accountant rather than assuming an update will only work in your favour.