Do students need tax numbers?

I am a 18 student. I've just matriculated and I'm planning to do casual work over the holidays. I was told I have to have a tax number on my CV in order to get work. Is this true?

It depends very much on what your earnings will be. If you will be earning below the tax threshold which is currently R73,650 per year, you don't need to pay tax and therefore don't need a tax number.