NOx Calculator Ireland 2026

Calculator

Enter your car's NOx figure (mg/km) and fuel type. The breakdown shows where each rate band kicks in and which cap (if any) applies. The result is the NOx component of your VRT only — add it to the CO₂-based VRT for the total payable. For the full Cat A calculation including CO₂ bands, BEV relief and Cat B / C / M paths, use the main VRT calculator.

How the Irish NOx levy actually works

The NOx levy on Cat A passenger-car VRT is a piecewise stepped charge, calculated per mg/km of NOx emissions from the Certificate of Conformity (CoC):

The rates are stepped, not bracketed. Each mg/km is taxed at the rate of the band it falls into. So a car with 90 mg/km NOx pays:

Not 90 × €25 = €2,250 (which would be wrong) and not €1,050 / €2,250 averaged into one rate (also wrong). The calculator above implements the stepped logic exactly.

The levy was introduced on 1 January 2020 by Finance Act 2019, replacing a flat 1% diesel surcharge that had run from 1 January 2018 to 31 December 2019. The new per-mg/km design produced larger revenues from older / dirtier diesels (where the 1% surcharge was the same as for a clean modern diesel) and slightly lower charges on clean post-Euro-6d engines. The rates and caps below have been unchanged since 2020; Budget 2026 made no adjustments.

Caps by fuel type

In practice, the petrol cap rarely engages — most modern petrol cars sit at 25–55 mg/km NOx, putting them well under €600. The diesel cap engages only on the worst older diesels (pre-Euro-5, or Euro-5s with broken / removed SCR). The €5,000 "no figure" cap is intentionally punitive: it discourages owners from claiming missing emissions data and pushes them to find or commission proper measurements.

Why NOx hits diesel imports hardest

Diesel engines produce more NOx than petrol engines under comparable load conditions. The reason is combustion chemistry: diesels run lean (excess air) at higher compression and higher peak-flame temperatures, both of which favour the formation of nitrogen oxides from atmospheric N₂. Petrol engines run closer to stoichiometric and at lower peak temperatures, producing fewer NOx but more CO₂ and CO per kilometre.

The regulatory response to diesel NOx has been three waves:

1. Euro 5 (2009–2014): limited NOx for diesels to 180 mg/km. Most pre-2015 diesel imports sit near this limit in real-world testing. NOx of 100–180 mg/km is typical for this era.
2. Euro 6 / 6b (2014–2017): cut the diesel NOx limit to 80 mg/km. Most cars met this with EGR (exhaust gas recirculation); the worse cars achieved the limit only on the type-approval bench (the "defeat device" scandal). Real-world NOx in this era often ran 200–600 mg/km on the road versus the 80 mg/km bench result.
3. Euro 6d / 6d-Temp (2017+): tightened limits and added Real Driving Emissions (RDE) testing on the road, plus mandatory SCR (Selective Catalytic Reduction with AdBlue). Modern Euro-6d diesels now achieve genuine 60–90 mg/km in real-world driving. Most 2018+ diesel CoCs show NOx in the 30–80 mg/km range.

The Irish NOx levy lands hardest on the middle wave — Euro-5 and early Euro-6 diesels (roughly 2011–2017 registrations) — which is precisely the import pool that UK price differentials encourage Irish buyers to look at. A 2014 BMW 320d at 130 mg/km NOx incurs €2,050 in NOx alone, on top of CO₂-based VRT typically already in band 19 at 35%. That's why these imports stopped making economic sense at current rates.

Typical NOx by Euro standard — quick reference

These are typical CoC ranges, not absolute. Specific cars vary; always check the actual CoC NOx figure (section V.3) before assuming a band. The trend is clear: a modern Euro-6d diesel pays meaningfully less NOx levy than a Euro-5 or Euro-6b version of the same car.

Worked examples — six 2026 NOx scenarios

1. Modern petrol family car (40 mg/km)

(40 × €5) = €200. Well under the €600 petrol cap.

2. Modern diesel SUV (60 mg/km, Euro 6d)

(40 × €5) + (20 × €15) = €200 + €300 = €500. Reasonable on a modern diesel.

3. Used Euro-5 diesel (130 mg/km)

(40 × €5) + (40 × €15) + (50 × €25) = €200 + €600 + €1,250 = €2,050. A meaningful chunk on top of CO₂-based VRT.

4. Old Euro-4 diesel (180 mg/km)

(40 × €5) + (40 × €15) + (100 × €25) = €200 + €600 + €2,500 = €3,300. Still under the €4,850 diesel cap.

5. Pre-Euro-5 diesel with no SCR (250 mg/km)

(40 × €5) + (40 × €15) + (170 × €25) = €200 + €600 + €4,250 = €5,050. Capped at €4,850. The diesel cap finally bites.

6. BEV (0 g/km, 0 mg/km)

€0. No tailpipe NOx, no levy.

Total VRT figures from these scenarios live in the main VRT calculator's worked-examples section. Add the NOx levy from above to the CO₂-based VRT for that car to get the total.

Where to find your car's NOx figure

• Certificate of Conformity (CoC), section V.3 — the authoritative source. Every EU-registered car has one; if you don't have it, the manufacturer's importer can issue a copy.
• Manufacturer's emissions document — many manufacturers publish per-variant emissions data on their corporate / technical sites.
• UK V5C does NOT show NOx — V5Cs show only CO₂. For UK imports you must obtain the original CoC from the manufacturer (Audi, BMW, Mercedes, Toyota and most volume brands operate Irish CoC services for €50–€100).
• Independent emissions test — accredited test centres can produce a certified NOx report (typically €300–€600). Useful for older cars or where the manufacturer cannot supply a CoC.
• NCTS export inspection — for the purpose of the export refund only, the NOx figure is taken from the existing Revenue record at first registration.

What happens if there's no NOx figure

Revenue applies the "emissions not established"rule: a flat €5,000 NOx levy. This is the highest possible charge under the scheme and is intentionally punitive — it discourages owners from claiming "no NOx data available" to avoid the levy and pushes them to find or commission proper measurements.

In practice, the €5,000 default applies in three situations:

• The vehicle's type-approval predates EU NOx publication requirements and the manufacturer cannot supply a CoC.
• The CoC has been lost or damaged and no replacement can be obtained.
• The vehicle is a one-off conversion, kit car or low-volume special where NOx was never type-approved.

In every case the owner has the option of commissioning an independent emissions test from an accredited centre — the €300–€600 cost is usually trivial compared with the €5,000 default.

Sources

• Finance Act 2019 — introduced the per-mg/km NOx levy from 1 January 2020.
• Revenue VRT Manual — current rates, caps and the "emissions not established" default.
• EU Regulation 715/2007 (Euro 5/6) and follow-ons — type-approval NOx limits.
• Real Driving Emissions (RDE) Regulation 2017 — on-road NOx testing for type-approval.
• citizensinformation.ie — VRT and NOx overview pages.

Frequently asked questions