NOx calculator — your levy in euro, in seconds flat
Enter your car's NOx figure in mg/km and its fuel type below, and the tool applies the official Revenue bands to return your NOx levy in euro — the emissions share of the Vehicle Registration Tax you pay to register a car in Ireland.
That charge runs from a few hundred euro on a clean petrol car to several thousand on an older diesel, which is exactly why you want the number before you commit to a purchase — not at the NCTS counter.
Estimates are indicative — the final levy is fixed by Revenue from the official NOx value on your Certificate of Conformity.
€5–€25
Per mg/km, three stepped bands
€4,850
Maximum levy on a diesel
€0
NOx charge on electric cars
What Is the NOx Levy and How Does the Calculator Work?
The NOx levy is an emissions charge added to your VRT when you register a car in Ireland, calculated per milligram of nitrogen oxide emitted per kilometre. It was introduced on 1 January 2020 under the Finance Act 2019, replacing the flat 1% diesel surcharge that had run through 2019.
The charge applies to every Category A vehicle — passenger cars and SUVs — whether they run on petrol, diesel or hybrid power. The figure itself comes from the emissions test behind the car's Euro 6 (or earlier) type approval. Fully electric cars (BEVs) produce no nitrogen oxide and are exempt. The rates and caps have not changed since 2020, and Budget 2026 left them untouched.
The calculator does the arithmetic for you. You supply two inputs:
From there it runs your emissions through the three-band scale and returns the euro charge, so you can budget with a real number rather than a guess.
NOx Charge Bands: €5, €15 and €25 per mg/km
The Irish NOx levy is charged at €5 per mg/km for the first 40 mg/km, €15 per mg/km from 41 to 80 mg/km, and €25 per mg/km for everything above 80 mg/km. Here is exactly how the charge is built up from your emissions figure.
| NOx emissions | Rate per mg/km |
|---|---|
| 0–40 mg/km | €5 |
| 41–80 mg/km | €15 |
| 81 mg/km and above | €25 |
The Charge Is Stepped, Not a Single Rate
The bands are stepped, which means each mg/km is taxed at the rate of the band it falls into — not at a single flat rate on the whole figure. A car emitting 90 mg/km does not pay 90 × €25. It pays €5 on its first 40 mg/km, €15 on the next 40, and €25 only on the final 10. Getting this cumulative logic right is the difference between a realistic budget and a nasty surprise, because a flat-rate guess overstates the charge badly.
Worked Example — One 2018 Discovery Sport, Two Very Different Bills
Take a 2018 Land Rover Discovery Sport 2.0 TD4, a diesel SUV imported from the UK. The same nameplate hides two common variants, and the Certificate of Conformity tells them apart: the TD4 150 with a manual gearbox, and the heavier TD4 180 automatic with all-wheel drive. Different NOx and CO₂ figures mean two very different registration bills.
Variant A — TD4 150, manual
| CoC NOx (section V.3) | 100 mg/km |
| NOx levy | €1,300 |
| OMSP determined by Revenue | €16,400 |
| WLTP CO₂ → band rate | 144 g/km → 21.5% |
| CO₂ component: 21.5% × €16,400 | €3,526 |
| Total VRT due | €4,826 |
Variant B — TD4 180, automatic AWD
| CoC NOx (section V.3) | 129 mg/km |
| NOx levy | €2,025 |
| OMSP determined by Revenue | €18,000 |
| WLTP CO₂ → band rate | 153 g/km → 27.5% |
| CO₂ component: 27.5% × €18,000 | €4,950 |
| Total VRT due | €6,975 |
How the levies are built. Variant A's levy stacks three slices: (40 × €5) + (40 × €15) + (20 × €25) = €200 + €600 + €500 = €1,300. Variant B carries 29 extra mg/km, every one of them in the top band: €200 + €600 + (49 × €25) = €2,025. Both sit comfortably under the €4,850 diesel cap — and both show why an older, higher-NOx diesel costs far more here than a modern petrol car.
The variant gap. Those 29 mg/km add €725 of levy on their own, and the 180's higher CO₂ band and OMSP push the total VRT difference to roughly €2,150. Two cars with the same badge on the tailgate, more than two thousand euro apart at the NCTS desk — check the exact variant on the paperwork before you agree a price.
NOx Caps by Fuel Type: €600, €4,850 and €5,000
Because the top band climbs quickly, Revenue caps the total levy — and the cap that applies depends on your fuel type. A punitive €5,000 charge applies when no NOx figure can be established at all.
| Fuel type | NOx cap |
|---|---|
| Petrol (incl. petrol HEV) | €600 |
| Diesel (incl. diesel PHEV) | €4,850 |
| Emissions not established | €5,000 |
| Battery electric (BEV) | €0 |
In practice the petrol cap rarely bites, because most modern petrol cars sit well below the emissions needed to reach €600. The diesel cap engages only on the worst older diesels. The one to watch is the €5,000 charge, applied when you cannot prove a NOx figure at all — a real risk on private imports, and unchanged in Budget 2026.
Where to Find Your Car's NOx Figure
The calculator is only as accurate as the number you enter, so it is worth knowing exactly where that figure comes from — and which document will let you down.
On the Certificate of Conformity (Section V.3)
The CoC is the manufacturer's certified emissions document, and the NOx value you need sits in section V.3. If your paperwork shows the figure in g/km rather than mg/km, convert it by multiplying by 1,000 — 0.100 g/km equals 100 mg/km. Entering g/km by mistake would understate your levy massively, so always confirm the unit before you calculate.
Unit check: a modern Euro 6 diesel often shows around 0.080 g/km, which is 80 mg/km — not 0.08 mg/km. Multiply any g/km figure by 1,000 before you type it in, or your estimate will be a thousand times too low.
Importing From the UK? The V5C Won't Show NOx
If you are importing from the UK, be aware that the V5C registration document does not list a NOx figure. You will need the manufacturer's Certificate of Conformity to get the correct mg/km value. Turning up to register without it risks the €5,000 "emissions not established" charge, so source the CoC from the manufacturer or a main dealer before your appointment.
Case in point: Conor bought a 2016 diesel estate in England and arrived at the NCTS with only the V5C. With no CoC to prove the NOx figure, he faced the €5,000 charge until he obtained the manufacturer's Certificate of Conformity, which showed 88 mg/km and brought his NOx levy down to €1,000.
How the Calculator Works, Screen by Screen
No account, no email, nothing to install — the whole run takes less time than finding your logbook. Here is what happens between your first click and the final figure.
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Open the Estimate Form
Scroll up to the calculator embedded at the top of this page and start a new estimate. It loads directly in the page, and there is no login step between you and the result.
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Tell It Where the Car Is Coming From
Pick the country of origin first — the UK, Northern Ireland or elsewhere. That single choice frames the rest of the estimate, because it determines how the import side of the bill is treated alongside the levy itself.
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Identify the Car
Type the registration plate if you have it, and the tool decodes the vehicle for you. No plate yet? Enter the make and model by hand instead — useful when you're still comparing listings and haven't settled on one car.
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Read the Instant Valuation
The screen returns the OMSP alongside the car's CO₂ and NOx figures, so you can see in one view how the emissions side of the tax stacks up against the value side — with the NOx levy already converted into euro.
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Keep the PDF Report
Download the estimate as a PDF and hold onto it. It gives you a dated, itemised reference to compare against the figure Revenue produces at your NCTS appointment — and a solid basis for questions if the two don't line up.
How NOx Fits Into Your Total VRT and Import Bill
The NOx levy is only one part of your VRT: your total Vehicle Registration Tax is the CO₂-based charge plus the NOx charge, and on a UK import you also pay 23% import VAT. When you bring a used car in and register it at the NCTS, the cost stack usually looks like this:
To put the scale in context, Revenue collected €948 million in VRT in 2024. For your own budget, add your NOx figure to the CO₂-based VRT to see the full registration cost before you buy.
NOx Levy FAQ
The practical edge cases Irish importers most often ask about once they have their basic charge — payment, refunds, exemptions and unusual vehicles.
Do hybrids and plug-in hybrids pay the NOx levy?
Yes. Hybrids and PHEVs are Category A vehicles, so the levy applies to them in full. A petrol hybrid is capped at €600, while a diesel plug-in hybrid falls under the €4,850 diesel cap. Only fully electric cars escape the charge entirely.
Did Budget 2026 change the NOx bands or caps?
No. The €5/€15/€25 bands and the €600, €4,850 and €5,000 caps have been in place since 1 January 2020, and Budget 2026 left every one of them untouched. Any figure you calculate today uses the same scale Revenue applies at registration.
When and where do I actually pay the NOx levy?
At your NCTS registration appointment, as one line inside the single VRT payment — the levy is never billed separately. Book the appointment within 7 days of the car arriving in Ireland and complete registration within 30 days to avoid penalties.
Does the NOx levy apply to a car already registered in Ireland?
No. The charge is collected once, at the vehicle's first registration in the State. Buying a second-hand car that already carries Irish plates involves no NOx levy, because whoever registered it first has already paid it.
Can I get the NOx levy refunded if I later export the car?
No. Under Revenue's Export Repayment Scheme you can reclaim part of the CO2-based VRT when a car is permanently removed from the State, but the NOx component is excluded from the scheme and is never repaid.
How is the levy worked out for heavy commercial vehicles?
Heavy-duty type approvals record NOx in mg/kWh rather than mg/km, and Revenue converts that figure at the point of registration. The calculator on this page works in mg/km, so use it for cars and SUVs rather than trucks or coaches.
Can I use this NOx calculator for imports from outside the UK?
Yes. The levy depends only on the NOx figure and the fuel type, never on the country the car comes from, so the estimate holds for a German, Japanese or any other import. What changes with origin is the rest of the bill: VAT and customs duty are assessed differently for EU and non-EU vehicles.
The Levy, in One Breath
Your NOx levy turns mg/km into euro on a stepped scale: €5 on the first 40 mg/km, €15 on the next 40, €25 above 80 — capped at €600 for petrol and €4,850 for diesel, with a €5,000 charge if no figure can be proven.
Pull the mg/km value from section V.3 of the Certificate of Conformity — never the V5C — check the unit, and run it through the calculator above before you agree a price. Then add the CO₂-based charge and 23% import VAT to see the full cost of putting the car on Irish plates.
Electric cars pay nothing. Older diesels pay the most. Everything in between is exactly what this page helps you pin down in advance.
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