17 January 2007 - Changes to the rules for calculating the appropriate percentage from 2008/09

The appropriate percentage is based on the car's approved CO2 emissions figure.

There are some supplements and reductions to take account of different fuels.

The rules governing the calculation of the appropriate percentage change in three ways with effect from 2008/09.

The lower threshold, the CO2 emissions figure which determines the appropriate percentage for all cars, is reduced from 140 to 135.

A new '10 percent band' is introduced for cars with a CO2 emissions figure of exactly 120 g/km or lower, the normal rounding does not apply to this figure. They are called 'qualifying low emissions cars' in the legislation, QUALECs for short. Diesel adjustments apply to QUALECs as to all others, but that is all; no other reduction which is available on other cars applies to QUALECs. As a result, the only acceptable figures for the appropriate percentage for QUALECs are 13 percent - cars to which the diesel supplement applies, and 10 percent - all other cars.

There is a new 2 percent reduction for cars manufactured to be able to run on E85 fuel, a mixture of 85 percent bio-ethanol and 15 percent unleaded petrol. They will be known as type G on forms P46 (car) and P11D. Other cars cannot run on this mixture without damaging the engine.