When a .biz domain is a good choice
Your exact business name is available on .biz
If the .com is taken and the .co.za is already registered by another local business, .biz can help you keep the cleanest version of your business name. That is usually better than adding hyphens, long words, or awkward location terms just to force another extension.
You mainly need a business-focused secondary domain
.biz is useful for campaigns, redirects, product microsites, or brand protection. You can point it to your main website, use it for a specific offer, or keep it so another company cannot register a confusingly similar business domain.
You sell to a wider audience
.co.za is excellent for South African trust, but it is clearly local. If you sell outside South Africa and cannot get the .com, .biz gives you a generic business extension without tying the domain to one country.
You can support it with a professional site
A .biz domain needs a strong first impression. Use HTTPS, a clean website, a proper business email address, clear contact details, and real service pages. The domain can open the door, but the site has to earn the trust.