Car Emissions Check UK — CO2, Euro Standard, and ULEZ
A vehicle's emissions data affects its road tax cost, eligibility for clean air zones, and resale value. Here is how to check it and what the numbers mean.
CO2 Emissions (g/km)
CO2 emissions are measured in grams per kilometre (g/km) and represent the vehicle's type-approval figure — the official value measured during certification, not real-world driving. This figure is held by the DVLA and returned in a free registration check.
For vehicles first registered before April 2017, road tax (VED) is calculated directly from CO2 banding. Lower CO2 means lower annual tax — vehicles below 100 g/km paid £0 in many years. For newer registrations, a flat rate applies after the first year regardless of CO2.
Euro Emission Standards
Euro standards govern NOx, particulate matter, CO, and hydrocarbon emissions. They are set at type approval and cannot be changed after manufacture:
- Euro 4 — petrol cars from approx 2006. Broadly ULEZ-compliant for petrol.
- Euro 5 — 2011 onwards (petrol and diesel). Diesel still fails ULEZ.
- Euro 6 — September 2015 onwards. Both petrol and diesel ULEZ-compliant.
- Euro 6d — 2020 onwards. Current standard, stricter real-world testing.
Clean Air Zones and ULEZ
London's ULEZ and other UK Clean Air Zones (CAZ) charge non-compliant vehicles daily fees. ULEZ charges £12.50 per day for cars that do not meet the required Euro standard. Several other UK cities operate CAZ with similar non-compliance charges. Check the specific zone's requirements before driving into them — most provide a free registration checker.
Frequently Asked Questions
How do I check the CO2 emissions of a car in the UK?
CO2 emissions (g/km) are recorded by the DVLA and returned in a free registration check at gov.uk/get-vehicle-information-from-dvla. You can also check via VEHIXA free check — the CO2 figure from the DVLA register is shown. This is the official type-approval figure used to calculate road tax (VED) bands.
What is a Euro emissions standard and how do I find it?
Euro emission standards (Euro 1 through Euro 6d) are EU regulations governing pollutants from vehicle exhausts. Most UK vehicles built from 2015 meet Euro 6 standard. The DVLA check returns the Euro standard for registered vehicles. Euro 6 petrol and diesel vehicles are exempt from many ULEZ and CAZ charges.
Does my car's emissions rating affect road tax costs?
For vehicles first registered on or after April 2017, road tax (VED) is based on fuel type and whether CO2 emissions exceed 0 g/km. Zero-emission vehicles (pure electric) pay £0 for the first year. For vehicles registered before April 2017, the annual VED rate is directly based on CO2 g/km banded ranges.
What is ULEZ and how do I check if my car is compliant?
The Ultra Low Emission Zone (ULEZ) operates in London. Non-compliant vehicles are charged £12.50 per day. Petrol cars must meet Euro 4 standard (registered after 2006 as a broad guide) and diesel cars must meet Euro 6 (registered after September 2015 as a broad guide). Check exact compliance using TfL's vehicle checker at tfl.gov.uk/ulez-checker.
Check CO2 and Euro standard for any UK vehicle
Enter any registration for DVLA emissions data, MOT history, and full vehicle details.
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