What is "khums"

n. A Shi'ite form of tax

In Islamic tradition, khums ( , literally 'one fifth') refers to the historically required religious obligation of Muslim army to pay one-fifth of the spoils of war, the booty collected from non-believers after a military campaign; this tax was paid to the caliph or sultan, representing the state of Islam.

In Sunni tradition, the scope of khums tax has been ghanim, which is defined as the spoils of war. In Shia tradition, states Abdulaziz Sachedina, the scope of khums tax has included, (1) booty (al-ghanima), (2) objects obtained from the sea (al-ghaws), (3) treasure (al-kanz), (4) mineral resources (al-ma'adin), (5) gainful earnings (arbaah al-makaasib, business profits), (6) the lawful (al-halaal) which has become mixed up with the unlawful (al-haraam), and (7) land which is transferred from a Muslim to a dhimmi (a free non-Muslim who is protected by a treaty of surrender) by the latter's purchase of it. The recipients of the collected khums have been the descendants of Muhammad and the Islamic clergy.

Khums is a 20% tax that must be paid on all items regarded as ghanima (, booty seized with war). There are differing legal traditions within Islam about what constitutes ghanima, and thus how far-reaching khums should be. In some jurisdictions, khums included a 20% tax paid on business profit and on minerals extracted in regions under the control of the state. Khums is different and separate from other Islamic taxes such as zakat and jizya.

There are differences of opinion about the scope of khums in Sunni and Shia sects of Islam, as well as who owns it and how the collected khums should be spent.