4 September 2012 at 20:52
Assuming you are going to not register a separate business and run it as a sole trader you would pay income tax in your personal name. You would need to split your incomes and expenses related to the "business" from your personal expenses. Treat them as if they are different. You would complete the "local income" section of your ITR12 - income tax return for the business related income and expenses.
You will have to complete an IRP6 at the end of August and the following February which is an estimate of your earnings and you will pay tax at those points - https://www.taxtim.com/za/what-is-provisional-tax-how-and-when.php?utm_source=Provisional+peeps&utm_campaign=1506f7e6a7-Provisional+tax+reminder+-+Period+01&utm_medium=email
Even if the earnings change from month to month you would pay tax like this.
Let me know if you have any other questions?