Alistair Darling will present his first budget since taking over the position of Chancellor from Gordon Brown on 12 March.
Indications from the Pre-Budget Report were that the most polluting vehicles could expect an increase in taxation, while incentives will be provided for cleaner cars.
It remains to be seen how AMAP rates will be affected, if at all, as they were not discussed in the PBR.
AMAP rates have been under review for over a year and are the tax-free amount that an employer can pay staff for using their own car on business.