The Basic Conditions of Employment Act sets the minimum at 21 consecutive days of annual leave on full pay for each 12-month leave cycle. Because that figure counts consecutive days rather than working days, it comes out at 15 working days for someone working a five-day week and 18 for a six-day week.
An alternative in the Act allows one day of leave for every 17 days worked, or one hour for every 17 hours, which is the more practical basis for part-time and irregular schedules. Your contract can be more generous than the minimum but never less, and any clause purporting to give less is simply unenforceable.
Leave has to be granted within six months of the end of the cycle it accrued in. Your employer can decide when you take it if you cannot agree, and can require it to be taken during an annual shutdown, but they cannot let it quietly vanish.
On termination, any leave still owed must be paid out, including leave accrued in the current incomplete cycle. Paying out leave instead of granting it during employment is not permitted, which surprises employers who treat it as a flexible benefit.