Also if you leave your money in the market/luno wallet then you can't pay tax on fictional profit, they can only tax you once the bitcoin is repatriated to your bank account and exchanged for fiat currency.
On Luno you have two wallets a ZAR wallet and a BTC one.
If you deposit 100K into the ZAR wallet then buy BTC. A month later you sell your BTC and now have 200K in your ZAR wallet. 100K profit. My assumption is at this point you still don't have to pay any tax. Only when you move that money from your ZAR wallet to a bank account will you need to pay tax on the 100K profit you made.
Is this how you understand this?