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- NOx Tax in Europe - Everything You Need to Know
NOx Tax in Europe - Everything You Need to Know
Find out how NOx tax works across the EU, where it applies, and what it means for used car imports.
You’ve heard about CO₂ restrictions and taxes when importing cars, but what about NOx tax?
This is a lesser-known charge that some EU countries apply based on a car’s nitrogen oxide (NOx) emissions. So, it’s another cost to cover, and it usually applies to older diesel models.
Knowing where NOx tax applies and how it’s calculated can help you estimate total costs more accurately and avoid surprises during resale, so let’s look at how it works across the EU.
NOx emissions regulations in EU - 2025
In 2025, NOx emissions across the EU are still mainly regulated through Euro standards and real-driving emissions (RDE) testing conducted by manufacturers.
The current rules state that:
- Most passenger cars need to meet Euro 6 NOx limits: that’s 80 mg/km for diesel and 60 mg/km for petrol.
- Since 2017, the EU also requires real-world testing (not just lab results) to make sure cars meet those limits on the road too.
- Many countries use the NOx value listed on the Certificate of Conformity (COC) to calculate environmental taxes, including the NOx charge.
So even though a few different rules apply, Euro class is still the easiest and most commonly used way to understand a car’s NOx emissions, and we’ll now see how the NOx limits compare by Euro class.
Comparison of NOx emission standards by Euro class
The most direct way you’ll come across NOx values is through the Euro emission class listed in a car’s documents, like in COC certificates.
These classes (Euro 4, Euro 5, Euro 6…) are used across the EU to define how much pollution a vehicle is allowed to emit, and this includes nitrogen oxides.
Euro classes, which set NOx levels, were first introduced to regulate new cars. However, they’re now also used to:
- Calculate environmental taxes
- Check zone access
- Decide if a vehicle qualifies for registration
Here’s how the NOx limits compare by Euro class, expressed in grams per kilometer:
|
Euro class |
NOx limit (diesel) |
NOx limit (petrol) |
|
Euro 4 |
0.25 g/km |
0.08 g/km |
|
Euro 5 |
0.18 g/km |
0.06 g/km |
|
Euro 6 |
0.08 g/km |
0.06 g/km |
Euro 7 will be introduced in 2026, but its NOx limits will stay the same as in Euro 6.
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How NOx charge works in practice: documents and payment
If you’re registering or importing a used car in a country that applies NOx tax, the process is usually straightforward as you only have to know the car’s emissions data.
Whenever you’re required to handle NOx charges, you’ll need the car’s Certificate of Conformity, so that’s the main document to prepare. If you don’t have one, you could use an equivalent document that shows the official NOx value in mg/km.
The payment of NOx charges varies by country.
For instance, in Ireland, there’s a standalone NOx charge. In other countries, however, NOx is covered through other taxes related to registration. Here’s an overview of how some EU countries handle NOx when it comes to used car imports and registrations.
► Austria
Austria doesn’t charge NOx tax on its own. Instead, it’s included in the NoVA registration tax, which is mainly based on the car’s CO₂ emissions and value.
► Germany
Germany doesn’t charge a NOx fee at registration, but NOx levels still matter because of its low-emission zones. These zones require vehicles to have an appropriate sticker based on their emissions standard (Euro class).
So, if you want a car to be allowed into most city centers, its NOx emissions need to be low enough to qualify for a green sticker.
Other countries with similar zones include France, Italy, Spain, Austria, and the Netherlands, but Germany stands out for its strict, nationwide system.
► Ireland
Ireland charges a separate NOx charge that’s part of the Vehicle Registration Tax (VRT). The amount depends on how much NOx the car emits, based on the value shown in the COC.
The more the car emits, the more you pay:
- €5 per mg/km for the first 40 mg
- €15 per mg/km for the next 40 mg
- €25 per mg/km for anything above 80 mg
Keep in mind that there’s a cap on the total charge, even if the calculated amount is higher. The cap is €4,850 for diesel vehicles and €600 for all others.
To get an accurate estimate before import, it’s a good idea to use an NOx calculator, like this one.
Will anything change in 2026?
The NOx charges that we’ve seen are currently based on Euro 6 standards and existing national tax rules. However, there are some changes ahead.
Starting in 2026, the EU will introduce Euro 7, a new emissions standard for all newly-approved car models.
The NOx levels will stay the same as in Euro 6 (0.08 g/km for diesel and 0.06 g/km for petrol), but the rules will get stricter in other ways.
There will be stricter real-world driving tests and new limits on brake and tire pollution.
So while the NOx numbers stay the same, Euro 7 will make car manufacturers prove that their vehicles meet those limits more reliably and in a wider range of real-world conditions.
Will NOx tax affect used car prices in the EU?
In most countries, there won’t be big shifts in car prices just yet.
Traders in Ireland have to be careful with older diesel imports, as the NOx charge can significantly increase the total cost if the car has high emissions.
In countries without direct NOx charges, traders should still consider how emissions affect where buyers can drive a car. If a car can’t enter low-emission zones, it may be harder to sell, so always check at least the Euro class before you buy a car for resale.
NOx tax - FAQ
► Which EU countries use NOx emissions for motor vehicle taxation?
Ireland and Austria cover NOx in their registration tax. Germany uses NOx data for environmental zones rather than taxation.
► What is the NOx tax?
It’s a charge based on a car’s nitrogen oxide (NOx) emissions, and it’s often applied during import or registration.
► What is the emission limit for NOx in the EU?
Limits vary by Euro class. For example, Euro 6 diesels must emit no more than 80 mg/km
(0.08 g/km).
► What is the NOx level for Euro 6?
Euro 6 limits are 80 mg/km (0.08 g/km) for diesel and 60 mg/km (0.06 g/km) for petrol.
► How is NOx tax calculated?
Each country has its own formula, which is usually based on the car’s NOx emissions (mg/km) stated in the COC.
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