Vehicle tax in Portugal — a cost you can reduce
ISV — Imposto Sobre Veículos — is Portugal’s vehicle registration tax, applied whenever a new vehicle is first registered or when an imported used vehicle enters the Portuguese system. It can represent a significant portion of the total cost of bringing a car into the country. What many people do not realise is that the Certificate of Conformity (COC) plays a central role in determining exactly how much ISV you pay — and, in some cases, whether you pay it at all.
How ISV is calculated
The ISV calculation is based on two main components: the engine’s cubic capacity and the vehicle’s official $\text{CO}_2$ emissions figure. Both values come directly from the COC. If the COC is unavailable or inaccurate, the tax authorities will use default or estimated figures, which almost always result in a higher tax bill.
The formula is progressive: higher displacement and higher $\text{CO}_2$ both push the rate up. Plug-in hybrid and electric vehicles benefit from specific reductions, which are also validated against data in the COC.
| CO2 emissions (WLTP, g/km) | ISV component — approximate band |
| 0 g/km (full electric) | Exempt from $\text{CO}_2$ component |
| 1 – 99 g/km | Reduced rate |
| 100 – 160 g/km | Standard rate |
| 161 – 250 g/km | Elevated rate |
| Over 250 g/km | Maximum rate |
Situations where ISV can be reduced or waived
Portuguese law provides for several ISV reduction or exemption scenarios, all of which depend on the data contained in the COC:
- Returning emigrants (repatriates)Portuguese citizens who have been living and working abroad for at least 12 consecutive months and are returning to Portugal permanently can apply for a full ISV exemption on one vehicle. The vehicle must have been owned and registered in their name for at least six months before the move, and the COC is required to confirm the vehicle’s identity and technical specifications for the customs authority.
- Low-emission and electric vehiclesElectric vehicles with zero $\text{CO}_2$ emissions are fully exempt from the $\text{CO}_2$ component of ISV. Plug-in hybrids with low electric range may qualify for partial reductions. In both cases, the exact figures come from the COC, so having the correct manufacturer document — rather than a dealer printout — is essential.
- Vehicles already registered in another EU member stateWhen a vehicle has already been legally registered and driven in another EU country, a partial ISV reduction applies based on the vehicle’s age and mileage. The COC is used alongside the foreign registration document to validate the original type approval and confirm that all data matches.
What happens if you do not have a COC?
Without a COC, the Portuguese tax authority (AT) and the IMT cannot verify the vehicle’s official $\text{CO}_2$ figure. In practice, they will fall back on a less favourable default calculation. This means you are likely to pay significantly more ISV than necessary. In the case of a returning emigrant applying for full exemption, the absence of a COC can delay or even block the entire application.
Some importers attempt to use other documents — such as data from the vehicle’s registration certificate in its country of origin, or information extracted from an online database — as a substitute for the COC. These are not accepted as equivalent by the Portuguese authorities and will typically result in the application being returned for completion.
Step-by-step: using your COC to claim ISV benefit
- Step 1 — Order the original COC from the manufacturer or from an authorised COC provider such as COC-Express.eu
- Step 2 — Gather all supporting documents: foreign registration certificate, proof of ownership, proof of residence abroad (for emigrant exemption), and transport documents
- Step 3 — Submit the customs declaration (DAV — Declaração Aduaneira de Veículo) to Portuguese customs together with your COC
- Step 4 — The AT calculates ISV based on the COC data; if claiming exemption, the relevant legal basis must be cited in the declaration
- Step 5 — Once ISV is settled (or exemption is confirmed), proceed to the IMT for vehicle registration and Portuguese plate assignment
The entire process can take between two and six weeks depending on the complexity of the case and the speed with which the COC is obtained. Planning ahead is strongly recommended.
2026 updates: what has changed?
From 2024 onwards, Portugal adopted WLTP (Worldwide Harmonised Light Vehicle Test Procedure) as the standard measurement cycle for $\text{CO}_2$ in ISV calculations, replacing the older NEDC figures. COCs issued since 2019 already include WLTP data, but older COCs may only show NEDC values. In these cases, a conversion factor is applied. Having the most up-to-date version of your COC — which manufacturers can reissue — ensures you benefit from the most favourable applicable rate.
Save on ISV — get your original COC today. Fast delivery, all major brands. Visit coc-express.eu
