Only once your business sales/turnover (not salary) in any 12 month period is expected to exceed R1 million does it become compulsory to register for VAT.
Alternatively, if your business needs a VAT registration number for tender or other contractual business purposes, then a voluntary VAT registration number may be obtained.
One of the basic requirements here would be proof that more than R50 000 in turnover / income has already passed through your business account.