By: Short answer: the annual IUC in Portugal depends on the vehicle category (registered before or after July 2007), the engine capacity, the CO₂ emissions and the year of registration. You pay it every year, in the anniversary month of the registration. To see what your car will cost, use our IUC calculator. If you are importing, IUC is the second tax: the first, paid once, is the ISV.
What IUC is and when you pay it in Portugal
IUC (Imposto Único de Circulação) is Portugal's annual road tax. It is owed by whoever is the registered owner — not the driver. The deadline is the anniversary month of the registration: a car first registered in March is taxed every March. On an imported car, the first IUC arrives once the Portuguese plate has been issued.
Do not confuse it with the ISV, which is paid once, at registration. How that one is calculated is explained in the 2026 ISV calculator guide.
Category A or Category B: the first thing to establish
The calculation changes completely depending on the date of first registration:
| Category | Registration | The calculation uses |
|---|---|---|
| A | Before July 2007 | Engine capacity + registration-year band |
| B | July 2007 onwards | Engine capacity + CO₂ + registration-year coefficient |
That is why two identical cars, one from 2006 and one from 2008, can owe very different IUC: the 2008 car enters the CO₂ component, the 2006 one does not. When buying used in Portugal, always check the date on the DUA before assuming a figure.
What you need to simulate the IUC
- Date of first registration — sets the category and the year coefficient.
- Engine capacity in cm³ — on the DUA.
- Fuel type — diesel carries its own surcharge in Category B.
- CO₂ in g/km — Category B only; from the DUA or the certificate of conformity.
With those four figures the IUC calculator returns the estimated annual amount.
Exemptions and special cases
- Fully electric: exempt from IUC.
- Vehicles over 30 years old recognised as historic: a reduced flat rate.
- Diesel (Category B): an additional pollution surcharge that varies with engine size.
- High CO₂: vehicles above a set emissions level also pay the adicional de IUC — in practice a large-engined petrol SUV can cost several times the annual tax of a small hatchback.
The expensive mistake: choosing the car without checking the IUC
The ISV is visible, because it is one big invoice. The IUC goes unnoticed — and it is the one that stays. Over five years, the IUC gap between a 1.0 and a large-capacity 2.0 diesel comfortably pays for a holiday. When you are choosing a model, always add ISV (once) + IUC × the years you intend to keep the car; that is the honest comparison. Our guide to what car to buy in Portugal in 2026 walks the segments with exactly this logic, and legalising an imported car shows where IUC enters the process.
If you would rather skip the maths, look at our stock that is already legalised on Portuguese plates, where the car's IUC is known up front.
Note: Clara Cars is an independent car sourcing and import service — not the tax authority and not a bank. Calculator figures are estimates based on the tables in force; the amount due is the one officially assessed for the specific vehicle.
Frequently asked questions
When is the IUC due?
In the anniversary month of the first registration, every year. If the plate dates from September, the IUC falls due in September. You pay it on the Portal das Finanças or at any tax office.
Who pays the IUC if the car is sold mid-year?
It is owed by whoever is the registered owner when the tax becomes due. That is why the change of ownership should be registered without delay after a sale — see used-car buying scams in Portugal for what happens when the registration is left open.
Does an imported car pay IUC in its first year?
Yes, from the moment it holds a Portuguese plate. IUC is independent of the ISV already paid at legalisation.
Do electric cars pay IUC?
No. Fully electric cars are exempt from IUC. Plug-in hybrids do pay, though usually less, because their declared emissions are lower.
Does IUC rise as the car gets older?
Not because the car ages: the coefficient depends on the year of registration, which is fixed. What changes from year to year is the annual update of the tables.