Seed phrase
Also known as: recovery phrase, mnemonic phrase
A list of words that backs up a wallet and can regenerate its private keys; it must be kept secret and offline.
Definition
A seed phrase (recovery phrase) is a human-readable list of words, usually 12 or 24, from which a wallet derives all its private keys. It is the master backup: anyone with it can restore the wallet and take the funds. It should never be entered into websites or shared with tools. For tax purposes it is irrelevant to share. You only ever provide public addresses or read-only keys.
Example
You write your 24-word seed phrase on paper and store it offline; you never type it into a tax app, which only needs your public address.
Primary sources for South Africa: browse the official documents