25 May 2013 at 20:37
You would need to complete an IT77 Income Tax Registration Form - Obtain a SARS Tax Number
If you invoice a company they will probably keep back about 25% before paying you the money. This they will hand over to SARS. At the end of the tax year you will complete and submit an ITR12 Income Tax Return and show all your income. If you still have to pay tax on the difference because you are over the tax threshold then SARS will let you know.