No, you have to be older than 21 years to write the adult matric exam (the amended senior certificate). There's nothing stopping you preparing for the matric exam by studying. Remember that the matric exam takes into account years 10 to 12 of studying, so you may have quite a bit of catching up to do. If you are wanting to write the adult matric exam , you need to make sure you have at least grade 9 and are older than 21 years when you write the actual exam.

It is possible to rewrite the matric exam. However, to write the amended senior certificate (ASC) you need to be older than 21 years. To find out what organisations offer can assist you in rewriting the exam, follow this link... Click here

The National Certificate (Vocation) - NC(V) could be an option for you. This qualification was intended to give workplace-based skill sets in a variety of in-demand South African job sectors increasing an individual’s employability. Not everyone is suited to an academic career and university study. What the NCV does is provide students the opportunity to acquire a specific set of skills that are suitable for the workplace. This means that even if students do not complete matriculation, they will have the opportunity to develop their talents and construct a successful career. They can even eventually obtain a matric equivalence with the added advantage of having learnt valuable workplace skills. In general, in order to obtain a National Certificate (Vocational), a student is required to take a total of 7 subjects. These include  3 fundamental subjects (Life Orientation, Mathematics or Mathematical  literacy, Language - usually English) and 4 vocational subjects, of which 3 are compulsory and 1 is optional. Read more about the NC(V) here.