Key figures — as of 2026-09-12: IMI reference construction value rises from €532/m² to €570/m² for 2026, a 7.1% increase — set by Portaria n.º 471/2025/1 of 26 December 2025 — the base value used in the IMI formula (construction value + 25% for land) rises from €665 to €712.50/m² — applies to Modelo 1 declarations filed from 1 January 2026 — first increase since 2023, after three years frozen at €532.
The figure that moves the tax bill
Portugal's Ministry of Finance has fixed the "valor médio de construção por metro quadrado" — the reference construction value used to calculate the taxable value of urban properties for IMI (Imposto Municipal sobre Imóveis) purposes — at €570 per square metre for 2026, up from €532. The price per square metre of construction, one of the elements considered in the formula for assessing urban properties for municipal property tax purposes, will be 570 euros in 2026, according to a decree published in the Official Gazette. The change was formalised in Portaria n.º 471/2025/1, published 26 December 2025.
This isn't an abstract technical footnote. It is one of the core inputs into the formula that produces a property's valor patrimonial tributário (VPT) — the tax value on which annual IMI, and the AIMI wealth surcharge for higher-value holdings, are actually calculated. The value that feeds into the urban property valuation formula had been rising since 2019 but had stayed unchanged since 2023.
How the number actually works
Under Article 39 of the IMI Code, the base value of a built property adds a land component set at 25% on top of the construction value itself. This adjustment translates into an increase of €47.5 in the base value considered for assessment purposes, which rises from €665 to €712.5. That €712.50 base figure then feeds into the wider VPT formula — multiplied by gross floor area and by coefficients for location, quality/comfort, and age (vetustez) that vary property by property and município by município.
Crucially, the update isn't retroactive across the board. The rule applies to all urban properties whose Modelo 1 declarations, as referred to in Articles 13 and 37 of the IMI Code, are submitted from 1 January 2026 onwards. In practice that means anyone completing new construction, finishing a major reconstruction, or triggering a reassessment (an avaliação) in 2026 gets valued using the higher €570 benchmark — not owners of existing homes whose VPT was already locked in under the previous figure.
Who actually feels this
For foreigners this lands squarely on three groups: those building a house from scratch (common among buyers in the Algarve, Alentejo and rural interior), those undertaking a substantial reabilitação of an older property in cities like Lisbon or Porto, and anyone whose property gets a fresh Finanças assessment — which can be triggered by a sale, a permit update, or a municipal review. Buyers relying on renovation-heavy purchases to access lower entry prices should factor this into their post-completion tax projections, not just the purchase-stage IMT and stamp duty costs already baked into the deal.
GrowIN's estimate: the raw €47.5/m² jump in base value, applied before location and quality coefficients, means a typical 150m² new-build or fully reconstructed house could see its underlying base value component rise by roughly €7,125 (150m² × €47.5) purely from this update — before the município's own location multiplier is applied, which can push the real VPT change several times higher in sought-after coastal or urban zones. On a mid-range IMI rate of 0.35%, that base-level shift alone points to a few extra tens of euros a year on the bill, with the final number depending entirely on the location and quality coefficients your local Finanças office applies.
"A 7% rise in the construction benchmark quietly raises the ceiling on what every new-build or renovated home in Portugal can be taxed on," says GrowIN Portugal Editorial.
What to watch next
Owners awaiting a reassessment or completing a build in 2026 should request a copy of the resulting VPT calculation from Finanças once issued, and check it against the coefficients published for their freguesia. This is also the moment to confirm your property's Modelo 1 filing status is current — délays in reporting completed works can compound future liability. For anyone weighing a renovation project or new-build against the sums involved, our tax and NIF hub covers how IMI, IMT and AIMI interact for foreign owners, and our property services team can help review a specific VPT calculation before you commit to a project.
The Comissão Nacional de Avaliação de Prédios Urbanos reviews this benchmark annually, so a further adjustment for 2027 is possible depending on construction-cost trends the Bank of Portugal and INE track through the year — worth checking again before locking in a build timeline.