Ireland · NOx levy · VRT 2026
The NOx emissions calculator that prices your diesel before you bid
Enter the NOx figure in mg/km from your Certificate of Conformity, pick the fuel type, and you'll see the exact euro levy Revenue adds to your Vehicle Registration Tax — the €5, €15 and €25 bands and the 2026 caps applied for you, free and with no email address asked.
A high-NOx diesel can add thousands of euro before the car is even on Irish plates. Run the number while you're still choosing the car — not at the NCTS counter, when it's too late to walk away from the deal.
How the Irish NOx Levy Calculator Works
The calculator applies Ireland's statutory NOx levy directly to your vehicle's certified NOx figure: enter the value in mg/km, choose the fuel type, and this Irish NOx tax calculator returns the euro charge added to your VRT. There are only two inputs, but both matter. The mg/km value is the certified nitrogen-oxide emission of your specific car, and the fuel type sets the cap that limits the final bill.
The levy applies to all Category A vehicles — passenger cars and SUVs — registered after 31 December 2019, whether petrol, diesel or hybrid (SIMI / Finance Act 2019). Fully electric vehicles are the only exception: with no tailpipe NOx, a battery electric vehicle pays €0.
- Input 1 — NOx value in mg/km: the officially recorded figure from the Certificate of Conformity, not a rounded estimate.
- Input 2 — fuel type: determines the applicable cap (€600, €4,850 or €0).
- Scope: every Category A car and SUV registered from 1 January 2020 onward.
- Watch the unit: the figure must be in mg/km, not g/km — the two differ by a factor of 1,000.
The Stepped €5 / €15 / €25 Scale — With a Worked Example
Ireland's NOx levy is progressive, not a flat rate: you pay €5 per mg/km on the first 40 mg/km, €15 on the next 40 (41–80), and €25 on everything above 80 — so most drivers overestimate it by applying the top rate to the whole figure. The single most common mistake importers make is multiplying their entire NOx figure by €25, so it's worth walking through how the bands actually stack.
Each rate applies only to the mg/km that fall inside its own band — the way income tax brackets work, not a single rate on the total. That is why a car at 90 mg/km is charged €1,050, not 90 × €25.
| NOx band (mg/km) | Rate per mg/km |
|---|---|
| 0 – 40 | €5 |
| 41 – 80 | €15 |
| 81+ | €25 |
Example — Common Scenario: 2018 Opel Insignia 2.0 CDTi From the UK
A large Euro 6 diesel is the classic import case, and trim matters even within one model. Here is the same 2018 Insignia 2.0 CDTi in two variants — the SRi manual with a certified NOx figure of 168 mg/km, and the heavier Elite automatic recorded at 174 mg/km — run through the stepped scale band by band.
| Band calculation | SRi manual — 168 mg/km | Elite auto — 174 mg/km |
|---|---|---|
| First 40 mg/km × €5 | €200 | €200 |
| Next 40 mg/km (41–80) × €15 | €600 | €600 |
| Above 80 mg/km × €25 | 88 × €25 = €2,200 | 94 × €25 = €2,350 |
| Total NOx levy | €3,000 | €3,150 |
Reading the result. The flat-rate mistake would give 168 × €25 = €4,200 for the SRi — €1,200 too high. And because €3,000 sits below the diesel cap of €4,850, the full stepped amount is charged; the Elite's €3,150 clears the cap too. Had either figure been high enough to exceed €4,850, the cap would take over.
This is exactly the kind of gap — a feared €4,200 versus an actual €3,000 — that reshapes an import budget before the buyer commits. Six mg/km of difference between two trims of the same car is worth €150 here, so always calculate from the exact variant on your Certificate of Conformity.
NOx Levy Caps by Fuel Type
The NOx levy is capped at €600 for petrol, hybrid and other fuels, at €4,850 for diesel vehicles, and at €0 for battery electric vehicles — with a punitive €5,000 charge where emissions cannot be established. Because the €25 band has no upper limit on the figure itself, the caps are what stop a high-NOx diesel from becoming an unlimited bill.
The diesel cap is the one that decides most import cases. An old, high-NOx diesel will almost always hit €4,850, which is why a poorly chosen import can quietly wipe out any saving on the purchase price. The €5,000 figure is the harshest and the least talked about: it applies when no valid NOx value can be produced at all.
| Fuel type | Maximum NOx levy |
|---|---|
| Petrol / hybrid / other | €600 |
| Diesel | €4,850 |
| Battery electric (BEV) | €0 |
| Emissions not established | €5,000 |
Where to Find Your Car's NOx Value
Your NOx figure in mg/km is recorded in section V.3 of the vehicle's Certificate of Conformity (CoC) — and importantly, the UK V5C logbook does not show it, so buyers of UK imports must request the CoC from the manufacturer. None of the rates or caps above matter until you have that one number, and finding it is where most importers get stuck.
Irish and EU-registered cars usually come with a CoC, but a car bought in Britain typically arrives with only a V5C, which lists CO2 but not NOx. That leaves you chasing the manufacturer or a main dealer for the CoC — a step worth doing before you pay, not after.
- Certificate of Conformity — section V.3: the definitive NOx figure in mg/km.
- UK V5C logbook: shows CO2 but not NOx — do not rely on it for this calculation.
- No CoC to hand: request it from the manufacturer or franchised dealer using the VIN.
- Buying at auction: ask for the CoC figure in writing before bidding, not after collection.
NOx Is Only Half of Your VRT
The NOx levy is one of two components of Vehicle Registration Tax: your total VRT equals the CO2-based charge plus the VRT NOx charge, so the levy calculated here is added on top of the CO2 figure, not instead of it. Knowing your NOx levy is only useful once you slot it into the full VRT bill you'll actually pay at registration.
The CO2 charge is calculated from the car's Open Market Selling Price (OMSP) and its CO2 band, while the NOx charge is the mg/km figure run through the stepped scale above. Add the two together and you have the VRT that Revenue collects before the car can be registered.
The Two-Part VRT Formula
- CO2 charge = OMSP × the applicable CO2-band rate.
- NOx charge = your mg/km figure through the €5 / €15 / €25 scale.
- Total VRT = CO2 charge + NOx charge.
- Budget for both: a low-emitting diesel with a modest OMSP can still carry a heavy total bill once a large NOx levy is stacked on top.
Typical NOx Figures by Euro Standard
As a rough guide, older Euro 5 diesels often record NOx well above 80 mg/km — pushing them into the €25 band and towards the €4,850 cap — while Euro 6d diesels with SCR after-treatment and most petrol cars tend to sit far lower, which is why the import year and emission standard matter so much. If you don't yet have the exact figure, the vehicle's emission standard gives a realistic sense of which band you're heading for.
The turning point is selective catalytic reduction (SCR), the AdBlue-based after-treatment that Euro 6d diesels use to strip out most NOx. Petrol cars generally emit far less NOx than diesels of the same age, so they rarely trouble the €600 cap.
| Vehicle & standard | Typical NOx position | Levy outlook |
|---|---|---|
| Euro 5 diesel (roughly pre-2015) | Frequently well above 80 mg/km | €25 band; a real risk of nearing the €4,850 cap |
| Euro 6d diesel with SCR (AdBlue) | Typically much lower | Usually well under the cap — the exact CoC figure still decides |
| Petrol / hybrid | Far lower than diesels of the same age | Usually well within the €600 cap |
These are indicative benchmarks only — the official value on the Certificate of Conformity is what Revenue charges, so treat the Euro standard as a first filter, not the final answer.
In Summary
Ireland's NOx levy turns the mg/km figure on your Certificate of Conformity into a euro charge through three bands — €5, €15 and €25 per mg/km — capped at €600 for petrol and hybrids, €4,850 for diesels and €0 for battery electrics. Never multiply your whole figure by €25: a 168 mg/km diesel owes €3,000, not €4,200.
Get the certified NOx value from section V.3 of the CoC (the UK V5C won't show it), check the unit is mg/km, and remember the levy is only half the story — total VRT is the CO2 charge plus the NOx charge.
This calculator gives an estimate of the NOx component under the 2026 scale; the final amount is determined by Revenue at registration from the officially recorded value. No personal data is required and the calculation is free. Reviewed by a vehicle-import and VRT specialist — last updated 2026.
Frequently Asked Questions
The edge cases of Ireland's NOx levy — missing figures, hybrids, heavy-duty vehicles and what Budget 2026 did (and didn't) change.
What happens if there's no NOx figure for my car?
Revenue falls back on the default maximum charge for your fuel type — €4,850 for a diesel, €600 for petrol and other fuels, and up to €5,000 where emissions cannot be established at all. Obtaining the Certificate of Conformity from the manufacturer or a franchised dealer using the VIN almost always works out cheaper than leaving the field blank.
Do hybrids and plug-in hybrids pay the NOx levy?
Yes. Hybrids and PHEVs are Category A vehicles and pay the levy on their certified mg/km figure exactly like any petrol or diesel car. The hybrid drivetrain earns no discount: the charge is based purely on the tailpipe NOx figure on the CoC, so a PHEV with a modest but non-zero value still pays.
How is NOx charged on heavy-duty vehicles?
Heavy-duty vehicles are treated differently: their NOx is measured and charged per unit of energy, in mg/kWh, rather than the mg/km used for light Category A cars and SUVs. The €5 / €15 / €25 stepped scale on this page should never be applied to a heavy-duty figure.
Did the NOx levy change in Budget 2026?
No. Budget 2026 made no changes — the stepped scale and the fuel caps are unchanged since the levy took effect on 1 January 2020 under the Finance Act 2019, with no adjustment for inflation or emission-standard drift.
Does the NOx levy apply to cars imported from Northern Ireland?
Yes. The levy is triggered by first registration in Ireland, so a used car from Northern Ireland or Britain registered from 1 January 2020 onward pays it on its certified mg/km figure. The origin of the car changes nothing; only the fuel type and the NOx value set the bill.
Can an older car escape the levy because it was built before 2020?
No. What counts is the Irish registration date, not the build year — a 2012 diesel registered here in 2026 still pays the levy in full. Older diesels tend to carry the highest NOx figures, which makes pre-2015 imports the most likely to run into the €4,850 diesel cap.
Is the NOx levy a recurring annual charge?
No — it is a once-off component of Vehicle Registration Tax, paid when the car is first registered in Ireland. It has no effect on annual motor tax, which is based on CO2, and the car never pays the NOx levy again when it is sold on within Ireland.