An NGO must register with SARS even if you are not going to register as a PBO. If you do not obtain PBO status from SARS, your organisation will be liable for Income Tax (if any income is received).
When applying to become a PBO, we suggest also applying for S18A status which will allow your organisation to issue S18A certificates. This will allow Donors (which are taxable entitities) to deduct their donations made to your organisation (subject to certain limitations).
The application can take two months before approval is granted, so it is best to start the process as soon as possible.