Praise be to Allaah.

There are two scenarios with regard to cars. One of them is when they are used for transportation and errands. There is no zakaah in this case, as is the case with a camel that is needed, or a donkey and so on, and as is also the case with furniture. In this case, cars which are kept because of need and transportation, even if they are numerous, are exempted from zakaah; the same also applies to cars for hire (taxis). And the same applies to large transportation vehicles which are kept in order to use them for transportation; there is no zakaah on them. 

The second scenario is where the cars are for sale, i.e., one acquires them to sell them and deal in them. In this case zakaah is due on them as they come under the same heading as other trade goods, and when one full hijri year has passed since the cash with which they were bought was acquired, zakaah must be paid on them, or when one full hijri year has passed since acquiring the car, if he bought it on credit, then he must pay zakaah on it according to its value. This is what is required. End quote. 

Shaykh ‘Abd al-‘Azeez ibn Baaz(may Allah have mercy on him)