Private key
Also known as: secret key
The secret cryptographic key that authorises spending from a crypto address; anyone with it controls the funds.
Definition
A private key is the secret number that signs transactions, proving ownership and authorising movement of crypto from an address. It must be kept secret. Whoever holds it controls the assets. Public addresses are derived from it. For record-keeping, you never share private keys with tax tools; instead you connect via read-only API keys or public addresses, which is enough to reconstruct transaction history.
Example
You import your wallet into a tax tool using a public address only, never the private key, so the tool can read but not move funds.
Primary sources for South Africa: browse the official documents