Know the rules in force, find out how it is calculated and how much more you will pay in Single Circulation Tax (IUC) in 2023.
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There is a tax that owners of cars or other motor vehicles are subject to – the Single Circulation Tax. Also known by the acronym IUCthis tribute acts as a compensation for the environmental cost and wear and tear on the roads caused by the circulation of vehicles.
Created in 2007, the IUC extinguished the Municipal Tax on Vehicles, Circulation Tax and Trucking Tax. That is, in the specific case of automobiles, it came to replace the old “car seal”.
But unlike the previous ones, this tax is levied on the ownership of the vehicle, so it only ceases to be paid when it is written off and its registration cancelled.
In most cases, the amount to be paid depends on the engine capacity, CO2 emissions, the type of fuel used and the age of the vehicle.
In addition to cars, motorcycles, mopeds, tricycles and quadricycles, as well as recreational craft and aircraft for private use, are also subject to payment of the IUC.
What category does the vehicle belong to?
To find out which tax rates your vehicle is subject to, you first need to identify the category to which it belongs.
As far as cars are concerned, the IUC code foresees four categories (A, B, C and D). Motorcycles, mopeds, tricycles and quadricycles are part of category E.
But all these vehicles are subject to the payment of tax.
Passenger cars and mixed-use vehicles with a gross weight of up to 2,500 kg, registered for the first time in Portugal or in a country of the European Union or the European Economic Area, since 1981 and until the date of entry into force of the IUC Codethat is, until June 30, 2007 (inclusive).
Passenger cars referred to in paragraphs a) and d) of paragraph 1 of article 2 of the Vehicle Tax Code and passenger cars for mixed use with a gross weight not exceeding 2,500 kg, whose date of first registration, in national territory or in a Member State of the European Union or the European Economic Area, after the entry into force of the IUC Codethat is, from 1 July 2007 (inclusive).
Goods and mixed-use cars with a gross weight of more than 2,500 kg, intended for the private transport of goods, for own-account transport, or for hire without a driver who has these purposes.
Goods and mixed-use cars with a gross weight of more than 2,500 kg, intended for the public transport of goods, transport for hire or reward, or rented without a driver for these purposes.
Motorcycles, mopeds, tricycles and quadricycles, as these vehicles are defined by the Highway Code, registered since 1992.
The IUC is also levied on pleasure craft and aircraft for private use. These vehicles are included, respectively, in categories F and G.
How is the Single Circulation Tax calculated?
The calculation of the IUC is based on the tax rates published annually in the State Budget and which vary according to the vehicle category. In 2023, count on a 4% increase in the Single Circulation Tax, mainly due to the increase in inflation.
In the case of passenger and mixed-use cars, there are two ways of calculating the tax.
So, for the vehicles registered up to June 30, 2007 (category A)the calculation is based on the type of fuel, cylinder capacity and year of registration, by category.
But we already vehicles registered from July 1, 2007 (category B)the calculation formula takes into account the type of fuel, year of registration, cylinder capacity and CO2 emissions, by category.
Let us see, by way of example, how the calculation for category B vehicles.
Step 1
To find out the amount of tax to be paid, firstly, you need to check the rates for the category, in this case B, and check which ones apply. Thus, after identifying the car’s displacement and CO2 emission scale, then add the respective rates.
| Displacement Scale (cubic centimeters) |
Fees (euros) |
CO2 scale (g/km) NEDC |
CO2 scale (g/km) WLTP |
Fees (euros) |
| Up to 1,250 | €30.87 | Up to 120 | Up to 140 | €63.32 |
| Over 1,250 up to 1,750 | €61.94 | Over 140 up to 180 | Over 120 up to 205 | €94.88 |
| More than 1,750 up to 2,500 | €123.76 | Over 180 up to 250 | Over 205 up to 260 | €260.07 |
| More than 2,500 | €423.55 | More than 250 | More than 260 | €353.01 |
step 2
If applicable, add the additional fee for CO2 emissions. But note that it is only intended for vehicles with the date of first enrollment after January 1, 2017.
| CO2 scale (g/km) NEDC |
CO2 scale (g/km) WLTP |
Fees (euros) |
| Over 180 up to 250 | Over 205 up to 260 | €30.87 |
| More than 250 | More than 260 | €61.94 |
step 3
The result of the sum of the previous installments will therefore have to apply the coefficient corresponding to the date of the first registration.
| year of acquisition | Coefficient |
| 2007 | 1 |
| 2008 | 1.05 |
| 2009 | 1.10 |
| 2010 and beyond | 1.15 |
step 4
If the car runs on diesel, there is also an additional IUC.
| Diesel – Displacement (cubic centimeters) |
additional fee (euros) |
| Up to 1250 | €5.02 |
| Over 1250 to 1750 | €10.07 |
| Over 1750 up to 2500 | €20.12 |
| More than 2500 | €68.85 |
Taking into account the steps described, let us now calculate the amount of tax to be paid for two specific cases of category B light vehicles.
Example 1
Car (category B) | enrolled in 2015 | gasoline | displacement of 988 cm3 | emissions of 103 g of CO2/km by NEDC measurements.
- Cylinder rate: 30.87 euros;
- CO2 emissions rate: 63.32 euros;
- Rate additional CO2: not applicable (registration is prior to January 1, 2017);
- Coefficient of year of first registration: 1.15;
- Additional gas fee: not applicable (the car runs on gasoline).
Amount of IUC payable = (30.87 euros + 63.32 euros) x 1.15 = 108.31 euros.
Example 2
Car (category B) | enrolled in 2020 | diesel | displacement of 1,928 cm3 | emissions 185 g of CO2/km by WLTP measurements.
- Cylinder rate: 123.76 euros;
- CO2 emissions rate: 94.88 euros;
- Additional CO2 fee: not applicable (emissions are less than 205 g/km in the WLTP test);
- Coefficient of enrollment year: 1.15;
- Additional gas fee: 20.12 euros.
Amount of IUC payable = (123.76 euros + 94.88 euros) x 1.15 + 20.12 euros = 271.56 euros.
Payment of Single Circulation Tax
Unlike the taxes that preceded it, the IUC is levied on vehicle ownership and does not depend on your use. Which means that it is mandatory even if the car is stopped, for example.
Thus, and only and only when the vehicle is scrapped and its registration cancelled, the payment of the tax is no longer due.
Who must pay the IUC?
Thus, the IUC must be paid:
- By the owners of the vehicles in whose name they are registered;
- By financial tenants;
- By other holders of purchase option rights under the lease agreement, for example, leasinglong-term rental (ALD) or renting (operational leasing of vehicles);
- By purchasers with retention of title;
- In the case of undivided inheritance by its representative, that is, by the head of the couple.
When must it be paid?
The Single Circulation Tax must be paid annually until the end of the enrollment anniversary monthwhich appears in the Single Automobile Document (DUA).
Already is pay the IUC for the first timebecause you bought a new or used imported car, you have 30 days after the deadline required for registration (which, currently, is 60 days from the registration date).
What if the car is sold? Who must pay the IUC?
If the registration of the transfer of ownership took place before the anniversary date
vehicle registration, payment must be made by the new owner.
However, if you sold your car and the change of ownership has not been registered, that is, if the vehicle is still in your name in the database of the Instituto dos Registos e Notariado (IRN), then it is up to you to tax payment.
How is the payment made?
Payment can be made through the Finance Portal, where an Multibanco reference is generated. But under certain specific conditions, it can also be paid at any treasury of the Tax Authority (AT).
How is it proven?
Contrary to what happened with the “car seal”, proof of settlement does not have to be placed on the vehicle window. It is therefore up to the Tax Authorities, through the crossing of data, to verify the payment of the tax. Even so, you must keep proof of payment with the vehicle documents.
And if you don’t pay?
Failure to pay the IUC results in the seizure or immobilization of the vehicle, as well as the circulation documents, until the missing payment is made (the tax, the resulting fines, as well as the costs of removing and storing the vehicle). .
In what situations is it possible to be free of payment?
The IUC Code exempts a number of vehicles (such as taxis, classic cars and fire trucks) and owners (people with a degree of disability equal to or greater than 60%) from paying this tax. There is also an exemption when the amount of the IUC to be charged is less than 10 euros.
Consult in the article below all the exemptions from the payment of the IUC provided for by law.
Article originally published in July 2019. Last updated in January 2023.
