19 December 2013 at 9:01am. As you say, the IRD rate is 77c per km, however the AA rates are also acceptable to the IRD, but are calculated on the type of vehicle. Hence, a small car up to 1.5 litre is 53.2c per km and the rate goes up depending on the car to $1.07 per km for a large car over 3.5 litres.201 Posts. 19 December 2013 at 9:18am. The AA rate for this car would be 64c per km. However, our rates are based on a car at the 3rd year of age where depreciation is a significant component.