You can claim an immediate deduction for a percentage of the price of the car (excluding GST). This should represent the proportion that you use the car for earning income (as opposed to personal use). The propoprtion of time that you use the car for earning income is called the 'taxable purpose proportion'. This ability to 'write off' assets applies for income producing assets with a cost price of less than $20,000.
James purchased a new car on 1 July 2015 for $18,000 (excl. GST). 50% of his use of the car is for a taxable purpose (e.g. ride sharing). James is therefore entitled to write off the asset by claiming an immediate deduction of $9,000. This represents the taxable purpose proportion of the cost price of the car.