Calculating Vehicle Registration Tax

Calculating the NOx charge

Basis of Charge

Nitrogen Oxide (NOx) emissions will be taxable beginning on 1 January 2020. The charge is applicable to all Category A vehicles excluding electrics but including hybrids. 

The NOx charge will be a component of vehicle registration tax as outlined below:

Carbon Dioxide charge + NOx Charge = Total VRT payable.

NOx is charged on the basis of milligrams per kilometre as recorded on the Certificate of Conformity. In the case of heavy duty vehicles this will be milligrams per kilowatt hour. 

Depending on documentation such as foreign registration certificates the figure may also be shown as grams per kilometre. This will not affect the tax due as Revenue will convert this to milligrams in the calculation at registration.


The NOx charge is not currently included on the VRT calculator. This means that the estimate presented by the calculator will not be the final amount due. Customers can determine the potential NOx levy for their vehicle by using this calculator. This will provide an estimate of the charge payable.

The attached spreadsheet may assist to identify your vehicle with its estimated NOx emissions value.

Amount due

The NOx charge will be calculated according to the following table:

Calculation of NOx charge
NOx emissions (NOx mg/km or mg/kWh)Amount payable per mg/km or mg/kWh

The first 0-60 mg/km or mg/kWh, as the case may be


The next 20 mg/km or mg/kWh or part thereof, as the case may be, up to 80 mg/km or mg/kWh, as the case may be


The remainder above 80 mg/km or mg/kWh, as the case may be


If satisfactory evidence of NOx emissions cannot be provided the following maximum charges will apply:

  • Diesel vehicles: €4,850
  • or
  • All others: €600

Examples of the VRT calculation