Paying the Imposto Único de Circulação (IUC) in Portugal in 2026 — A Practical Guide to the Six Categorias, the Cilindrada/CO₂ Brackets, the Adicional for Diesel, EV and Disability Exemptions and the Birth-Month Window Before the 2027 April Switch

The Imposto Único de Circulação (IUC — Single Circulation Tax) is the annual Portuguese motor-vehicle tax owed by the registered owner of every car, motorcycle, light goods vehicle, heavy goods vehicle, recreational boat and private aircraft that holds a Portuguese matrícula (number plate). The rules sit in the Código do IUC, originally enacted by Lei 22-A/2007 of 29 June and consolidated through subsequent Orçamento do Estado revisions. 2026 marks the last calendar year on the legacy birth-month payment cadence: from 1 January 2027, IUC migrates to a unified April payment regime with two-or-three-instalment plans for higher-value vehicles. This guide covers the live 2026 mechanics first and the 2027 switch second.

The Six Categorias

The Código do IUC slots every taxable vehicle into one of six categorias. Each categoria has its own tax formula:

• Categoria A — light passenger cars (ligeiros de passageiros) and mixed-use vehicles first matriculated between 1981 and 30 June 2007. Tax depends on cilindrada (engine displacement), fuel type and year of registration. CO₂ emissions do not enter the formula.
• Categoria B — light passenger and mixed-use vehicles first matriculated from 1 July 2007 onward, and light goods vehicles under 3,500 kg in the same period. Tax depends on cilindrada and CO₂ emissions. This is the largest category — most cars in private use in 2026 sit here.
• Categoria C — heavy goods vehicles over 2,500 kg. Tax depends on weight and number of axles.
• Categoria D — heavy passenger vehicles (buses, coaches). Tax depends on weight, number of axles and emissions class.
• Categoria E — motorcycles, tricycles, quadricycles and mopeds matriculated from 1992 onward. Tax depends on cilindrada.
• Categoria F and Categoria G — recreational boats (Categoria F) and private-use aircraft (Categoria G). Tax depends on horsepower (boats) or maximum take-off weight (aircraft).

How Categoria B Is Calculated (the Big One)

For most residents, the relevant categoria is B and the relevant variables are cilindrada and CO₂. The 2026 tables are unchanged from 2025 — the Orçamento do Estado 2026 (Lei 82/2024 of 31 December) did not adjust the IUC rates.

Cilindrada component (Categoria B):

• Up to 1,250 cm³: €31.77
• 1,251 to 1,750 cm³: €63.83
• 1,751 to 2,500 cm³: €127.66
• Over 2,500 cm³: €435.84

CO₂ emissions component (Categoria B): brackets switch depending on whether the vehicle was certified under NEDC (typical for matrícula between July 2007 and August 2018) or WLTP (for matrículas from September 2018 onward). Representative WLTP brackets:

• Up to 140 g/km: €65.15
• 141 to 205 g/km: €99.86
• 206 to 260 g/km: €212.04
• Over 260 g/km: €441.74

The two components are added together, then multiplied by an age coefficient. The age coefficient ranges from 1.00 (vehicles matriculated in 2007) to 1.15 (vehicles matriculated from 2010 onward). The final figure is the headline IUC bill.

Adicional de IUC (the Diesel Surcharge)

Diesel-fuelled Categoria B vehicles carry a separate surcharge layer on top of the cilindrada and CO₂ components — the Adicional de IUC. The four 2026 brackets:

• Up to 1,250 cm³: €5.02
• 1,251 to 1,750 cm³: €10.07
• 1,751 to 2,500 cm³: €20.12
• Over 2,500 cm³: €68.85

The Adicional was introduced in the Orçamento do Estado 2017 to internalise the externality cost of diesel particulate emissions. Hybrid and plug-in hybrid vehicles do not pay the Adicional even if their internal combustion engine runs on diesel — the carve-out is explicit in the Código do IUC.

Exemptions and Special Cases

Three groups of vehicles fall outside the IUC perimeter or carry a partial exemption:

• Electric vehicles (EVs): fully exempt from IUC under both Categoria A (pre-2007 EVs, where the threshold is voltage rather than cilindrada) and Categoria B (post-2007 EVs). The exemption is universal — there is no upper voltage or kW cap. Plug-in hybrid vehicles are not exempt; they pay full Categoria B tax including the CO₂ component.
• Classic vehicles: matrículas more than 30 years old that meet the heritage-vehicle conditions set out in Decreto-Lei 64/2018 and the Federação Portuguesa de Veteranos do Automóvel guidance qualify for a 50% reduction. Strict use limits apply — the vehicle cannot serve as the household's daily driver.
• Disability holders: residents with an Atestado Médico de Incapacidade Multiusos (AMIM — Multi-Use Medical Disability Certificate) rated at 60% or higher qualify for full IUC exemption on one Categoria B vehicle up to €240 of annual tax. The exemption is renewed each year through Portal das Finanças → Veículos → Comunicações → IUC.

Smaller-cilindrada Categoria E motorcycles (mopeds and lighter motos) and vehicles owned by public bodies, foreign embassies, IPSS and rural fire-brigade associations also sit outside the standard IUC perimeter under separate Código do IUC provisions.

The 2026 Payment Window (Birth-Month Cadence)

For 2026, IUC must be paid by the end of the calendar month in which the vehicle was first matriculated. A car first registered on 14 March 2018 pays IUC by 31 March every year; a car first registered on 27 November 2022 pays by 30 November every year. The Autoridade Tributária issues a courtesy email reminder ~30 days before the deadline to the address on file, but the legal obligation runs on the owner regardless of whether the reminder arrives.

The payment flow runs through the Portal das Finanças (portaldasfinancas.gov.pt). The exact steps:

1. Log in with NIF and senha or with the Chave Móvel Digital (CMD) — see the CMD activation path if you have not yet activated it.
2. Navigate to Todos os Serviços → Veículos → IUC.
3. Enter the vehicle's matrícula and the year for which the IUC is owed.
4. The portal returns the IUC amount and issues a Documento Único de Cobrança (DUC) with payment references.
5. Pay through Multibanco (ATM or homebanking with the entidade/referência fields), through CTT post offices, through a serviço de Finanças counter, or through the portal's direct MB Way option.

The DUC is the legal proof of payment alongside the bank receipt — both should be kept on file (digitally or printed) for at least four years (the Lei Geral Tributária prescription window on tax dossiers).

Late Payment — Coimas and Juros

Missing the deadline triggers the contraordenação fiscal regime under the Regime Geral das Infrações Tributárias. Coimas (administrative fines) range from 15% to 50% of the unpaid IUC, with statutory minimums of €25 (negligence) and €50 (deliberate omission) for individuals. The Autoridade Tributária also applies juros de mora (default interest) on the overdue principal at the rate set monthly by the Ministério das Finanças (the May 2026 rate is 8.158%).

If the IUC is not settled within the contraordenação window, the file moves to execução fiscal — a debt-collection track that can lead to the matrícula being suspended in the IMT system and, in extreme cases, to penhora (seizure) of the vehicle. The fastest way out is to pay the principal, the coima and the juros at once through the Portal das Finanças.

Tribunal Constitucional's 2026 Decision on Sold Vehicles

On 4 June 2026, the Tribunal Constitucional overturned the Supremo Tribunal Administrativo's earlier reading of Article 3 of the Código do IUC and restored the rebuttable presumption that the registered owner on 1 January of the tax year is the taxpayer. Former owners who sold the vehicle before 1 January but did not update the registo automóvel can now formally rebut the Autoridade Tributária's IUC claim by showing the sale contract (contrato de compra e venda) and the buyer's acknowledgement of receipt. The decision is a meaningful change of guard for residents who sold an old vehicle without ever migrating the matrícula — the older Supremo ruling had blocked rebuttal entirely.

The 2027 April Switch

The Orçamento do Estado 2026 confirms the long-trailed migration from the birth-month cadence to a single annual payment window in April 2027. The structure:

• IUC under €100 → single April payment.
• IUC of €100–€500 → two instalments, April and October.
• IUC over €500 → three instalments, April, July and October.

Owners may always opt for a lump-sum April payment regardless of bracket. The reform's stated aim is to simplify the cash-flow workload on households with multiple vehicles and to align IUC with the IMI municipal property tax cadence (also April, May and August in 2026). 2026 remains the last year on the legacy regime — owners with a December matrícula should not bank on a free pass next year just because the deadline shifted; the AT will issue 2027 transition guidance over the coming Q4.

Profile-Based Checklists

Single-Car Household, 2018 Petrol Renault Clio 1.0 (Categoria B)

• Cilindrada: 999 cm³ → €31.77 cilindrada component.
• CO₂ (WLTP): ~120 g/km → €65.15 CO₂ component.
• Age coefficient: 1.15 (matrícula from 2010).
• Total IUC 2026: approximately €111.50.
• Pay by end of matrícula month through Portal das Finanças.

Family Household, 2020 Diesel Renault Mégane 1.5 dCi (Categoria B)

• Cilindrada: 1,461 cm³ → €63.83 cilindrada component.
• CO₂ (WLTP): ~140 g/km → €65.15 CO₂ component.
• Adicional Diesel: €10.07.
• Age coefficient: 1.15.
• Total IUC 2026: approximately €159.00.

EV Household, 2023 Tesla Model 3 (Categoria B)

• Fully exempt under the EV carve-out. No DUC owed.
• Owner should still log in to Portal das Finanças annually to confirm the exemption flag is active. Hybrids do not qualify.

Disability Household, 2021 Citroën C3 with AMIM ≥60%

• Total IUC 2026 below the €240 ceiling → fully exempt.
• Submit the AMIM and the IUC exemption request through Portal das Finanças → Veículos → Comunicações → IUC every year before the matrícula-month deadline.

Classic-Car Household, 1984 Renault 5 GT Turbo (Categoria A, over 30 years)

• Cilindrada: 1,397 cm³ → low Categoria A petrol bracket.
• Heritage 50% reduction applies if conditions met (limited use, no daily driver).
• Total IUC 2026: under €30 with the reduction.

Recently Sold Vehicle, Old Renault Mégane Transferred in November 2025

• If the registo automóvel was updated to the buyer before 1 January 2026, the AT bills the buyer and no action is needed.
• If the registo was not updated, the AT bills the previous owner. After the 4 June 2026 Tribunal Constitucional decision, the previous owner can rebut by uploading the sale contract through Portal das Finanças → Veículos → Comunicações.

What This Means for Expats

• Recent arrivals importing a foreign vehicle: IUC starts the year of matrícula in Portugal — there is no retroactive exposure to years before the Portuguese registration. The matrícula-month deadline applies from year one.
• Cross-border workers with a Spanish-registered vehicle: no IUC owed in Portugal as long as the vehicle remains on Spanish plates and the use stays within the cross-border-residence framework. Conversion to Portuguese plates triggers IUC from the matrícula date.
• EV buyers: the IUC exemption is one of the larger long-tail benefits of the EV-versus-hybrid choice and stacks with the lower IRS tax exposure on company-provided EVs versus combustion company cars. The exemption does not have a sunset clause in 2026.
• NHR and IFICI holders: the special tax regime IRS exemptions do not extend to IUC — IUC is owed on the Portuguese matrícula regardless of whether the owner's other income is on a reduced rate.
• Vehicle-sale planning: always update the registo automóvel through IMT immediately on sale and obtain the buyer's signed contrato de compra e venda. The Tribunal Constitucional 2026 decision restores rebuttal rights for prior years but does not displace the registo as the authoritative source of taxpayer identity.

2026 is the final calendar year of the legacy birth-month IUC cadence. Owners should pay this year's IUC as usual and watch for the Autoridade Tributária's 2027 transition portaria over Q4 — the April 2027 unified deadline will be the first cash-flow shift in the IUC framework since the 2007 Categoria B reform.