Understanding the NOx Charge Ireland: How Nitrogen Oxide Emissions Affect Your Vehicle Registration Tax

The NOx charge is a tax on nitrogen oxide (NOx) emissions that forms part of Vehicle Registration Tax (VRT) in Ireland. Introduced on 1 January 2020 by the Revenue Commissioners, this levy applies to every motor vehicle classified as a Category A vehicle — including passenger cars, SUVs, and hybrids — but vehicles excluding electrics. Whether you are buying new cars at a dealership or importing a used car from the UK, understanding this charge is essential to estimate the total VRT payable before you pay. This guide covers the nitrogen oxide NOx emissions rates, how the levy is calculated per milligram, and where to find the relevant reading from the vehicle’s manufacturer.

What Is the NOx Charge in Ireland?

The NOx levy is a charge payable on the registration of any VRT Category A vehicle in Ireland. It was made taxable beginning 1 January 2020, replacing the former diesel surcharge from Budget 2019. Under the Vehicle Registration Tax VRT framework, the charge nitrogen oxide — specifically nitrogen oxide (NOx) — is measured in milligrams per kilometre (per mg km or milligrams per kilowatt hour for heavy duty vehicles) as recorded on the Certificate of Conformity.

In practice, calculating Vehicle Registration Tax now involves two components: the CO₂ charge (based on the open market selling price and the vehicle’s carbon dioxide emissions) plus the NOx element. The formula is simple:

CO₂ Component + NOx Component = Total VRT Payable

This means the NOx element directly increases the tax owed on registration, making it critical for buyers to check their vehicle’s NOx value before committing to a purchase or import.

Which Vehicles Are Subject to the NOx Charge?

The levy is applicable to all Category A vehicles registered in Ireland after 31 December 2019. This includes:

• Passenger cars and SUVs (petrol and diesel)
• Hybrids (standard and plug-in hybrid — PHEVs)
• New vehicles purchased from dealers and used car imports from the UK, Northern Ireland, Japan, or elsewhere

Fully electric vehicles (BEVs) are exempt. No NOx figure applies to electrics, and they also qualify for a separate VRT relief of up to €5,000.

NOx Charge Rates: The 2026 Rate Table

The NOx charge is calculated cumulatively. Revenue applies a per mg/km matrix to the officially recorded manufacturer emissions levels. The current rates, in effect since 1 January 2021, are:

The levy is cumulative: a vehicle producing 60 mg/km of NOx would pay €5 on the first 40 mg (= €200) plus €15 on the remainder of 20 mg (= €300), totalling €500. Any part thereof above a band threshold triggers the higher rate.

Maximum NOx Caps: Diesel vs Other Vehicles

To limit the charge on high-emission vehicles, the Revenue Commissioners have set maximum caps:

If satisfactory evidence of the NOx figure cannot be provided, the flat maximum is applied automatically. This is particularly relevant for imports where foreign registration certificates may not contain the emissions data. For diesel vehicles, this means the full €4,850 for diesel vehicles cap — making proper documentation essential.

How to Calculate the NOx Charge (Step by Step)

Using a NOx calculator is the fastest way to estimate the levy, but understanding the manual calculation helps you verify any result. Here is the process:

• Step 1 — Find your NOx figure. Locate the emissions reading on the Certificate of Conformity (CoC) or the vehicle’s foreign registration certificates. The figure is typically expressed in g/km (grams per kilometre). Multiply by 1,000 to convert to mg/km.
• Step 2 — Apply the rate bands. Use the three-band table above to calculate the cumulative charge. Each band is applied to its portion only.
• Step 3 — Add to the CO₂ component. The CO₂ charge is determined by applying the VRT rate (based on WLTP CO₂ g km value) to the open market selling price (OMSP). Add the NOx result to get VRT payable.

If the reading on your documents is in grams per kilometre, Revenue will convert it to milligrams at registration. This does not affect the tax due.

Calculation Example: Diesel Import (VW Golf TDI)

Calculation Example: Petrol Import (Toyota Corolla)

These examples show how dramatically the levy differs between diesel and petrol engines. A VRT calculator that includes the NOx component — such as the official tool on ros.ie or third-party tools like Cartell’s NOx calculator — can provide a quick estimate for your specific car.

Where to Find Your Vehicle’s NOx Emissions Figure

One of the most common challenges for buyers is locating the NOx figure for their specific car. The nitrogen oxide (NOx) emissions data is not always obvious, and different vehicles require different sources. Always check with the vehicle’s manufacturer if other documents are unavailable. Here is where to look:

UK Imports: The V5C and the Missing NOx Figure

Many UK V5C registration documents issued after April 2019 no longer display the NOx value in box V3. If your document lacks this data, contact the vehicle’s manufacturer or a main dealer to request the Certificate of Conformity. An eCOC can be uploaded directly through Revenue’s online process. Without valid documentation, the flat charge will be applied at the NCTS centre.

Tools like Cartell’s NOx emissions finder and various online VRT calculator services can help identify NOx emissions by car model, often using just the registration number. These are particularly useful for quickly screening potential imports before purchase.

NOx Charge History: From Budget 2019 to 2026

The NOx levy has evolved since Budget 2019. Understanding the timeline helps clarify which rates are applicable to your registration date:

The rate structure has remained stable since 2021, giving buyers certainty when calculating Vehicle Registration Tax for current-year registration.

NOx Charge for Hybrids, PHEVs and Electric Vehicles

The interaction between the NOx levy and different powertrain types is frequently misunderstood. Here is how each category is treated:

• Full electric vehicles (BEVs): Completely exempt from the NOx levy. No NOx emissions means no charge payable. BEVs also qualify for VRT relief of up to €5,000, tapered for vehicles with an OMSP above €40,000 and disappearing entirely above €50,000.
• Plug-in hybrids (PHEVs): Subject to the levy like any other petrol or diesel vehicle. PHEVs typically have low NOx value readings (often under 20 mg/km), resulting in modest charges. VRT relief for PHEVs was available until end-2020 (for those with CO₂ under 65 g km).
• Standard hybrids: Also chargeable. Emission levels depend on the combustion engine component. Most modern hybrids produce relatively low NOx, keeping the amount under €100.

In all cases, the NOx figure must be sourced from the certificate or equivalent documentation. Even low-emission hybrids need valid proof to avoid the flat charge.

Frequently Asked Questions About the NOx Charge

What is the NOx charge in Ireland?

The NOx charge is a component of Vehicle Registration Tax (VRT) that taxes the nitrogen oxide (NOx) emissions of a motor vehicle. It is calculated based on certified emission levels in milligrams per kilometre and added to the CO₂ component to form the total VRT.

Is the NOx charge included in VRT?

Yes. The NOx levy is one of two components of VRT. The total VRT payable equals the CO₂ charge plus the NOx amount. For new cars bought at a dealer in Ireland, this is already included in the sale price. For imports, you must pay it separately at the NCTS centre during registration.

How is the NOx charge calculated?

The calculation uses a cumulative three-band system: €5 per mg/km for the first 40 mg, €15 for the next 40 mg (up to 80 mg km), and €25 for the remainder above 80 mg. Maximum caps apply as outlined in the rate table above.

What is the maximum NOx charge for diesel vehicles?

The cap for diesel vehicles is €4,850. This flat maximum is also applied if no valid emissions documentation is provided at registration. For petrol, hybrid, and other non-diesel vehicles, the maximum is €600.

Do electric vehicles pay NOx?

No. Fully electric vehicles (electrics) are exempt as they produce zero nitrogen oxide emissions. They also qualify for a separate VRT relief. However, hybrids and PHEVs are not exempt — they are chargeable based on their combustion engine emissions.

Where can I find my car’s NOx emissions figure?

The primary source is the Certificate of Conformity (CoC) issued by the vehicle’s manufacturer. For UK imports, the reading may appear in box V3 of the V5C. If not available, request a CoC from the manufacturer or main dealer. Revenue will also accept official written confirmation on a case-by-case basis.

What happens if I cannot prove my vehicle’s NOx level?

If you cannot provide evidence of your vehicle’s NOx emissions, the Revenue Commissioners will apply the maximum flat charge (see caps in the rate table above). This is why obtaining the Certificate of Conformity or foreign registration certificates with the relevant data before booking your NCTS centre appointment is essential.

Does the NOx charge apply to commercial vehicles?

The NOx levy applies specifically to VRT Category A vehicles (passenger cars and SUVs). VRT Category B (light commercial vehicles) and Category C (heavy commercial) are taxed differently, with a flat rate or percentage of OMSP. For further information on commercial vehicle registration, check the Revenue website.

Useful Resources and Official Links

• Revenue.ie — Official NOx levy page with current rate bands and calculation examples
• ROS.ie — Official VRT calculator including NOx estimation
• NCTS.ie — Book your VRT registration inspection appointment
• Cartell.ie — Free NOx calculator and NOx emissions finder by registration
• SIMI.ie — Industry guidance on motor tax, VRT rates, and the levy from the Society of the Irish Motor Industry

Disclaimer: This guide is for informational purposes only and does not constitute tax or legal advice. Always verify the latest rates and requirements on Revenue.ie before making financial decisions. Rates and reliefs are subject to change in future Budgets. Last updated: March 2026.