Vehicle Circulation Tax 2026 – IUC Simulator

The Portuguese road tax is the annual tax you pay for having a vehicle registered in your name. It comes back every year, for as long as the registration stays with you. That is the difference that matters against ISV, which is paid once only, at the first registration in Portugal: ISV is the cost of getting in, IUC is the annual rent that follows.

It is paid by whoever is on the ownership record on the day the tax falls due — there is no split between seller and buyer and no refund of months. If you sell the car, deal with the ownership record without waiting: while the registration is still in your name, the IUC is still yours, even if the car has been in somebody else’s garage for months.

The tax is not the same for every vehicle either. The IUC Code sorts them into categories, and it is the category that decides which sum applies — a flat table amount, a sum of engine size and CO₂, or gross weight and nothing else.

• Categories A and B: passenger cars and dual-purpose cars up to 2,500 kg. The date of first registration decides which of the two applies.
• Categories C and D: goods vehicles over 2,500 kg. Category C is private or own-account carriage, category D is public carriage.
• Category E: motorcycles, mopeds, tricycles and quadricycles registered from 1992 onwards.
• Outside this simulator: categories F and G, boats and aircraft, which have rules of their own and nothing in common with the ones above.

If you are bringing a used vehicle in from abroad, count on two bills rather than one: first the ISV, settled with the customs declaration before you can get Portuguese plates, and then the IUC, every year from that point on.

The IUC tax period is not the calendar year. It starts on the registration date and starts again on each of its anniversaries, and the tax is due in full — there is no pro rata by month and nothing is ever refunded. So the practical question is not "how much do I pay a month", it is "whose car is it on the day the tax falls due".

The deadline is the last day of the anniversary month of the registration. A car registered on the 14th of March pays in March, by the 31st, every year. The month does not change when the car is sold or when you move house: it is tied to the registration. Anyone with two or three vehicles has two or three different months to keep track of — and no letter ever arrives about any of them.

On a newly registered vehicle a different rule applies. The IUC Code allows 30 days counted from the end of the legal deadline for filing the ownership record. That registration deadline is set by another statute, not by this code, so confirm it before you start counting days — the real deadline is the sum of the two, and it is that sum that gets quoted in conversation as if it were a single round number.

Miss the deadline and the tax does not go away: late-payment interest accrues, non-payment is an administrative offence that can lead to a fine, and the debt ends up in tax enforcement, with costs. The amounts depend on the tax owed and on how late the payment is, so they are not part of this simulation.

• Every year, in the same month: the anniversary of the first registration. Set a reminder on your phone — nobody is going to warn you.
• By the last day of that month. Interest starts running on the first day of the month after it.
• Several vehicles, several months: each registration has its own, and there is no way to merge them into one.

From 2027 the calendar changes. A change has been approved that takes IUC off the anniversary month of the registration and moves it to fixed months of the year, with October as the reference in the first year and the payment split up on the larger amounts. It touches neither the rates nor the bands: what moves is the date. Until that change takes effect, the deadline is the one described above.

Everything this simulator asks for sits in one place: the vehicle documents. Nothing has to be looked up elsewhere — and nothing has to be estimated. If you are sizing up a car that is not yours yet, ask the seller for a photograph of the registration certificate; it is information any owner has to hand, and it gives nothing personal away once the document number and the address are covered.

European registration certificates use harmonised field codes that are the same in every country, and they are the fastest way to find each figure. The certificate of conformity (COC) that comes with a vehicle brought in from abroad carries the same information.

• Date of first registration — field B. This is the one that weighs most: it decides the category, the year coefficient and the month you have to pay in. On a car brought in from another European Union or European Economic Area country, what counts is the first registration there, not the Portuguese one — the IUC Code speaks of vehicles registered "in national territory or in a Member State of the European Union or of the European Economic Area". Which is why a 2016 German import does not become a new car by changing its plates.
• Engine size — field P.1, in cubic centimetres. It is the figure that separates the engine-size bands, and one cubic centimetre more is enough to jump a band.
• CO₂ emissions — field V.7, in g/km, or the equivalent figure on the COC. It is only asked for in category B. Check whether it is expressed under NEDC or under WLTP before you use it — there is a whole block on that further down, right after the tables.
• Gross weight — the gross weight line of the certificate, field F.2 on harmonised documents, in kilograms. It only matters to goods vehicles, and only above 2,500 kg, which is where categories C and D begin.
• Fuel — field P.3. On a hybrid, what the simulator needs to know is what the combustion engine burns, because that is what decides the diesel surcharge.

One input is on no document at all: the type of carriage of a goods vehicle. Until public carriage is evidenced, private carriage is presumed — category C — and that is the option the simulator starts on.

The IUC Code came into force on the 1st of July 2007 and brought a new calculation with it. Cars registered up to the end of June 2007 stayed in category A, on the old sum; those registered from the 1st of July 2007 onwards are in category B, on the new one. Same statute, two completely different calculations — and it is the date on the document that decides, not how old the car looks.

Category A: a table amount, and nothing else. Three things are crossed — the fuel, the engine size and the band of registration years — and the table returns an annual amount. There is no CO₂, no coefficient, nothing that climbs with age. A 1600 cc petrol car registered in June 2007 pays €62.40 a year.

Category B: a sum of four parts. Engine size plus CO₂, plus the CO₂ surcharge if the registration is from 2017 onwards, all of it multiplied by the year coefficient — and, if the vehicle runs on diesel, the diesel surcharge on top. That same 1600 cc petrol car, with 160 g of CO₂/km under NEDC, registered one month later in July 2007, pays €161.37. One month of difference on the registration, almost €99 a year apart — every year, for good.

• The category A sum: fuel × engine size × band of registration years → a table amount.
• The category B sum: (engine size + CO₂ + CO₂ surcharge) × year coefficient + diesel surcharge.
• Categories C and D: gross weight only. No engine size, no CO₂, no coefficient.
• Category E: engine size and a band of years, in just two columns.

One detail of category A trips a lot of people up: the diesel column already has the diesel-vehicle surcharge folded into it. A 1900 cc diesel from 1998 shows up as €46.26, which is €39.95 of base rate plus €6.31 of surcharge. An LPG car of the same engine size and the same year uses exactly the same engine-size bands but stops at €39.95, because the surcharge only reaches vehicles that run on diesel. That second figure follows from reading the statute: it puts LPG and natural gas in the "other fuels" column alongside diesel, then restricts the surcharge to diesel vehicles — the public calculators consulted do not even offer LPG in category A, so check how your vehicle is classified if that is your case.

NEDC and WLTP are two different test cycles for measuring the emissions of the same car. WLTP is the newer one and the closer to real driving, so it returns higher CO₂ figures for the same vehicle. The IUC Code does not convert one into the other: it gives each of them bands of its own, side by side, as the CO₂ component table just above shows.

That is why the choice is not a detail. The same number of grams falls into different bands depending on the cycle. On a 1600 cc car registered in 2015 with 130 g/km, the simulator returns €148.22 if you tell it WLTP and €185.58 if you tell it NEDC — €37.36 a year apart, off the same line of the same document. Try it above: that field is the only thing that changes between the two sums.

The simulator starts on WLTP, which is the sensible default on a recent car. On an older one it is exactly the wrong answer, and it is the one that understates the tax — which is why it is worth checking before you calculate rather than after the assessment lands.

• The document decides. If the registration certificate or the COC labels the CO₂ figure as WLTP, it is WLTP; if it labels it NEDC, it is NEDC. Do not guess from the age of the car when the paper is in front of you.
• Before 2018 there is no doubt: WLTP was not yet the homologation cycle, so a car from back then carries NEDC figures. That covers most of the category B fleet on the road.
• On recent cars it is WLTP: it is the cycle that replaced the older one, and it is what the documents issued since then carry.
• In between, look at the paper. Through the transition years, roughly 2018 to 2020, documents with a correlated NEDC figure sit alongside documents already on WLTP. That is where the mistake happens.
• Do not convert by hand. There is no fixed factor that turns one cycle into the other, and an estimated figure lands the car in the wrong band as easily as it would land it in the right one.

If you still cannot tell after all that, run both sums and budget for the higher one. It is the only one of the two that cannot surprise you when the assessment arrives, and the gap between them tells you exactly what the uncertainty is worth.

The category B sum has an order, and the order matters: the year coefficient multiplies some parts and leaves one out. Here it is on a real car — a plain 1968 cc diesel, 155 g of CO₂/km under NEDC, first registered in June 2019. Put those values into the simulator above and you should land on exactly the same figure.

If that same car ran on petrol it would stop at €258.73: the diesel surcharge is, to the cent, the difference between the two.

• 1. Engine-size component. 1968 cc falls into the 1,750 to 2,500 cc band: €127.35.
• 2. CO₂ component. 155 g/km under NEDC falls into the 120 to 180 g/km band: €97.63.
• 3. CO₂ surcharge. It only exists above 180 g/km under NEDC — 205 g/km under WLTP — and only on registrations from 2017 onwards. This car is a 2019, but it sits below the band: €0.
• 4. Year coefficient. Registered in 2010 or later, coefficient 1.15, applied to the three parts above: (127.35 + 97.63 + 0) × 1.15 = €258.73.
• 5. Diesel surcharge. It comes from a different statute, not from the IUC Code, and therefore lands outside the coefficient: 1968 cc pays €20.12, added at the end. Total: €278.85.

The CO₂ surcharge is still missing from that example. Swap the car for a 2996 cc petrol with 250 g/km under WLTP, registered in August 2022: that is €435.84 of engine size, €212.04 of CO₂ and €31.77 of surcharge, because 250 g/km under WLTP falls into the 205 to 260 band and the registration is after 2017. The three parts add up to €679.65, which the 1.15 coefficient lifts to €781.60. The same car registered in 2016 pays no surcharge and stops at €745.06 — the €36.54 between them is the €31.77 surcharge already multiplied by the coefficient.

A separate note on hybrids, and on what it rests on. The surcharge statute falls on "vehicles running on diesel", without the word "exclusively" that the same statutes use elsewhere when they mean exclusivity. Read that way, it also catches a hybrid whose combustion engine burns diesel, and leaves out a petrol hybrid — that is the reading this simulator applies, and it is why it asks anyone who picks a hybrid what the engine burns. It is a reading of the statutory text rather than confirmed practice: none of the public calculators consulted during the research can even express a diesel hybrid, so there is no way to cross-check it against a third party. If that is your case, confirm the fuel recorded on the vehicle registration before relying on the figure.

The IUC Code uses two different words for two different effects, and the confusion between them explains half the questions about this tax. Under an exemption, no tax is due: there is nothing to assess. Under a waiver of collection, the tax is due and is assessed — it is simply not collected, because the amount came in below €10. The simulator shows the two cases with different messages; take note of which one you get.

There is a third case as well, which also produces a zero and is neither of those: vehicles the tax never reaches in the first place. A car registered before 1981 and a motorcycle registered before 1992 are outside categories A and E — they are not exempt, there is simply no table they fit into.

• Fully electric: exempt, in every category. The provision granting this exemption names no category, unlike the ones on either side of it, which name theirs. It therefore covers cars, motorcycles and mopeds, and it covers an electric vehicle registered before July 2007 too. Many people assume it only reaches cars: it does not stop there.
• Disability rated at 60 % or above: exemption limited to one vehicle per beneficiary in each year and to a maximum of €240, for category B cars up to 180 g of CO₂/km under NEDC or 205 g under WLTP, and for categories A and E.
• Vehicles over 30 years old: exempt where the competent authorities recognise them as being of historic interest, they are only occasionally used, and they do not travel more than 500 km a year. The provision names categories A, C, D and E.
• Taxis and chauffeur-driven hire: exempt in category A and, in category B, up to 180 g of CO₂/km under NEDC or 205 g under WLTP.
• Below €10: waiver of collection. The tax is assessed, but there is no collection of any kind. The threshold is strict: €9.99 is not paid, €10.00 is.

The 125 case. A 125 cc motorcycle registered in 2015 carries a real rate of €6.19 a year and pays nothing, because the waiver catches it. It is not exempt, it is waived — and the difference stops being academic the day the table rises above €10. At the other end of the scale, no category B car can ever fall into the waiver: the arithmetic minimum is €31.77 of engine size plus €65.15 of CO₂ at coefficient 1.00, that is €96.92, nearly ten times the threshold.

Category E covers motorcycles, mopeds, tricycles and quadricycles registered from 1992 onwards, and it has only two year columns: up to 1996 and after 1996. A 600 from 2015 pays €63.62 a year; the same 600 registered in 1994 pays €37.47; a 1200 from 2015 pays €138.15.

Two quirks of this table. Below 120 cc there is no band at all, in any year: a 110 cc moped has no rate. And motorcycles of 120 to 250 cc registered between 1992 and 1996 pay €0.00 because that is what the table in article 13.º prints in that cell — it is not the €10 waiver, it is a zero rate written into the statute. The same 125 registered in 2015 does have a rate, €6.19, which the waiver then cancels. Different mechanisms, and the simulator reports them with different messages.

Categories C and D apply to goods vehicles over 2,500 kg of gross weight, and the sum is weight alone: no engine size, no CO₂, no coefficient. What separates the two is the type of carriage, and the gap is large. At 3,000 kg it is €58.21 for private carriage against €15.77 for public carriage; at 8,000 kg, €226.24 against €59.80. Until public carriage is evidenced, private carriage is presumed, so category C is what you get by default.

From 12,000 kg upwards this simulator is no use, and it is better said here than in the result panel. At that level articles 11.º and 12.º trade the weight table for matrices combining the number of axles, the suspension type of the driving axles and the year of first registration of the tractor unit — hundreds of amounts and four inputs this form does not collect. If your vehicle weighs 12 tonnes or more, the simulator refuses the calculation instead of inventing a figure.

There are also two 50 % reductions that do not appear here because they depend on case-by-case certification: categories C and D operating exclusively within one autonomous region, and category C vehicles above 3,500 kg used for travelling fairs or touring shows.

IUC is self-assessed: no letter ever arrives to remind you. It is the owner who logs into the Portal das Finanças, issues the collection document for the vehicle and pays it by ATM reference, through online banking or over the counter. There is no paperwork in the post, no notice and no direct debit quietly doing it for you.

The collection document is issued from the registration number, and that is where you confirm which month the tax authority has on record for your vehicle. It is worth doing once, unhurried, before a deadline is breathing down your neck — it is the quickest way to find out that the month you assumed is not the month on file.

• Before buying used: run the IUC with the engine size, the CO₂ and the registration date shown in the listing. Two similar cars can sit in different categories and pay twice what the other one pays.
• After selling: confirm the ownership record has changed hands. Until it does, the tax is yours.
• With more than one vehicle: issue the collection documents separately. Each registration has its own month and its own reference.

A tax assessed below €10 is not collected: in that case there is nothing to pay, and it is not a sign that something went wrong on the portal.

This simulator is a tool to help you plan, not an assessment. It applies the IUC Code tables in force in 2026 to the details you enter and shows the sum broken down so you can follow it line by line — but the amount you have to pay is the one the Portuguese tax authority assesses on the Portal das Finanças, from the vehicle registration data.

The result is only as good as the inputs. One wrong digit in the engine size, a CO₂ figure from the wrong cycle or a registration month one out changes the band and changes the total — sometimes by more than a hundred euros a year. Check every field against the vehicle document before you make any decision on the number shown here.

Some situations are deliberately not modelled: the exemptions and reductions that depend on case-by-case recognition, goods vehicles from 12,000 kg upwards, and categories F and G. In those cases the simulator refuses the calculation or points at the rules, rather than returning an approximate figure that would look like an answer.

AUTO.MOTO.pt accepts no responsibility for decisions taken on the basis of this simulation. If in doubt, check on the Portal das Finanças or with a certified accountant.