If you are paid a per kilometer allowance and the flat rate (under 37.03 f) of the CBA) both your per kilometer allowance and your flat rate will appear as a taxable benefit in Box 14 of your T4 slip.
If your vehicle allowance is reported in Box 14 of your T4 slip, your employer is required to fill out form T2200 (Declaration of Conditions of Employment) and you are entitled to fill out form T777 (Statement of Employment Expenses) when you file your income taxes to claim employment expenses related to your vehicle. Vehicle related expenses go on line 22900 (other employment expenses).