WLTP: The Worldwide Harmonised Light Vehicle Test Procedure

The way new vehicles are tested for carbon dioxide (CO2) emissions and fuel consumption is changing. As of 1 September 2017, all new models of car have to undergo the Worldwide Harmonised Light Vehicle Test Procedure (WLTP), which replaces the New European Driving Cycle (NEDC). From 1 September 2018, all new cars will have to be certified under the new system.

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What is the WLTP?

The WLTP is a laboratory test that measures a car’s fuel consumption and its emissions of CO2 and air pollutants. It has been designed to be more representative of real-world driving than the outdated NEDC test that was introduced in 1992 and last updated in 1997.

The WLTP is now longer, lasting 30 minutes instead of 20 and covering 14.4 miles instead of 6.8. The car is driven faster, with both a higher average speed and a higher top speed than under the NEDC. The test also features more realistic driving behaviour – such as more rapid acceleration and more sudden braking – across a wider range of road types. And the WLTP takes into account the effects of optional equipment on both emissions and fuel efficiency.

The aim is to produce figures for fuel consumption and CO2 emissions that more closely reflect a car’s actual performance on the road. This will improve the information available to customers looking for a new car and enable them to make a more informed choice. And, because a number of taxes and other fees are linked to a car’s CO2 emissions, it may also affect how much you have to pay.

How the WLTP will affect your taxes

For both Company Car Tax (CCT) and first-year Vehicle Excise Duty (VED), cars are put into bands depending on their CO2 emissions. The cleanest cars pay the lowest rates and the most polluting ones pay the highest. If a car’s official emissions figure is higher under the new system, it may therefore incur higher rates of CCT and first-year VED.

In addition, the amount of Corporation Tax relief that a business can claim on the cars it buys or leases also depends on their emissions. To qualify for the 100% first-year allowance for low-emission cars that is available until 31 March 2021, a car must emit no more than 50g CO2/km. And to be eligible for the 18% main rate of tax relief – or to avoid the 15% ‘lease rental restriction’ – a car must emit no more than 110g CO2/km. The switch to WLTP may see some cars pushed over one of these thresholds.

The change may also affect whether certain models are classified as ultra-low emission vehicles (ULEVs), and this may in turn have an impact on the vehicle’s costs. ULEVs are exempt from paying the Congestion Charge in central London, they are eligible for free parking in some cities, and the Government offers grants towards the cost of most plug-in ULEVs. To qualify for these incentives, a vehicle must emit less than 75g CO2/km. If a car is pushed over that threshold under the new system, it will no longer be classified as a ULEV and will lose entitlement to these benefits.


The switch to WLTP figures for CO2 emissions will not happen immediately. The changeover for CCT and VED will occur in April 2020. Until then, the Government will continue to use NEDC figures.

However, as of September 2018, new cars will undergo the WLTP but not the NEDC. They will therefore have their WLTP results converted to NEDC-equivalent figures for tax purposes, using a simulation model called 'CO2MPAS'. The NEDC-equivalent figures generated by CO2MPAS may be slightly different to those obtained for the same model in actual NEDC tests.

Impact on drivers and fleets

  • You will see fuel consumption and CO2 emissions figures that more accurately reflect how the car actually performs on the road.
  • You may have to pay a different first-year VED rate.
  • You may have to pay a different CCT rate.
  • Some cars that are currently classified as ULEVs may lose that status. If so, they will no longer be eligible for the plug-in car grant, exemption from the Congestion Charge or free parking in certain places.
  • For organisations operating a fleet, the amount of Corporation Tax relief you can claim on your vehicles may change.

However, no vehicles registered before 1 September 2017 will be affected by WLTP.

Download the guide today.


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