Khums is obligatory on the following seven things:
1. Profit or gain from earning.
2. Minerals.
3. Treasure trove.
4. Amalgamation of Halal wealth with Haraam.
5. Gems obtained from the sea diving.
6. Spoils of war.
7. As commonly held, a land which a zimmi (a non-Muslim living under the protection of Islamic Government) purchases from a Muslim.