How IUC is calculated in Portugal
IUC (Imposto Único de Circulação) is paid every year. It depends on the first-registration date: cars from July 2007 onward (Category B) use engine size + CO₂; older ones (Category A) use engine size only. Here is the calculation — with open code to verify.
Step by step
- Category by registration date — B (≥ July 2007): engine size + CO₂; A (older): engine size only; E: motorcycles.
- Category B — an engine-size component + a CO₂ component, multiplied by the year coefficient.
- Diesel surcharge — an add-on for diesel vehicles.
- CO₂ add-on — an extra for cars registered 2017 onward above an emissions threshold.
- Fully electric — exempt from IUC.
See it with an example
Open this example in the calculator →
Sources & verification
Based on the official Autoridade Tributária (AT) tables, cross-checked June 2026. It's a maintained estimate — not a substitute for the official AT simulator or a despachante. The calculation is open source (MIT): github.com/claracarspt/calcs.
Road tax (IUC) · How ISV is calculated in Portugal · ISV & IUC