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HMRC internal manual

Employment Income Manual

HM Revenue & Customs
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Car benefit: special cases: employees with frequent changes of car (from 2009/10): Averaging Step 4: average CO2 emissions and appropriate percentage of notional car

EIM23815 explains why the arrangements described on this page exist and EIM23825 explains how the guidance on them is laid out.

This page follows from Step 3, described at EIM23845.

STEP 4A: average CO2 emissions for the notional car in each group

This is achieved using this process:

  • ignore any cars in a group which do not have a CO2 emissions figure
  • take the CO2 emissions figure of each other car in the group, as determined at Step 1 (EIM23830) and add these together
  • add 15 for each diesel car in the group to which the diesel supplement applies (EIM24805)
  • for 2009/10 and 2010/11 only, for cars which are not QUALECs (i.e. have CO2 emissions figures of 121 g/km or higher, EIM24605):

    • deduct 15 for each hybrid
    • deduct 10 for each bi-fuel (type B, EIM24830) car or car manufactured to run on E85 (type G, EIM24840)
  • now bring any cars which do not have a CO2 emissions figure back into the calculation by adding the figure obtained from EIM23835 
  • divide the result by the number of cars in the group

The result is the CO2 emissions figure for the notional car in that group (round down to the next integer).

STEP 4B: find the appropriate percentage for the notional car

Because the effect of all fuels other than petrol has been taken into account in the above calculation, the notional car is deemed to run on petrol.

The appropriate percentage for the year is therefore determined using the ready reckoner at EIM24700 or EIM24705 (as appropriate) without the need for any further adjustments.

Step 5 follows at EIM23855.

2008/09 and earlier years

This guidance applies only for 2009/10 and later years. Local arrangements applied for years to 2008/09 as described at EIM23750 onwards.