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HMRC internal manual

Gas for road fuel use

Technical Guidance: Gas measurement

You should ascertain the methods proposed for measurement of gas. Where a measurement forms the basis of a commercial transaction, it may normally be accepted as correct. If measurement is necessary for revenue purposes the best practicable method is to be adopted; consider the possibility of fitting a flowmeter where appropriate. Confirm the agreed method of measurement in writing to the trader.

To calculate the duty payable gas must be measured by mass (per Kilogram). If gas is recorded by volume or cubic metre, calculation of the dutiable quantity should be done using the following conversion factor which have been agreed with the relevant trade associations/suppliers:

  • Compressed Natural Gas (CNG)At atmospheric pressure (approx. 1 Bar) 1 cubic metre of natural gas has a mass of 0.76 kilograms.

For road fuel use natural gas is subject to high compression in order to minimise the size of the storage tank on the vehicle.

If the amount of gas supplied to either compressed storage or directly to the vehicle is measured by mass then that figure (in kilograms) should be used for duty accounting.

If the measurement is by volume then the volume must be converted to mass for the duty rate to be applied.

The measured volume of gas in cubic metres should be multiplied by 0.76 (as above) and again by the pressure in Bar in order to arrive at the mass for excise duty.

You should refer to the manufacturer’s specification (and any calibration reports) for the particular compression and dispensing equipment used in order to confirm the pressure at which the gas is delivered.

  • Liquefied Petroleum Gas

  • 1 Litre contains 0.500 Kilograms.1 Kilogram is contained in 2 Litres.

  • Liquefied Natural Gas

  • 1 litre contains 0.592 Kilograms.1 Kilogram contains 1.689 litres.

For conversion factors for any other type of gas, contact the UoE for clarification and guidance.