Only the Shiahs believe in this additional tax and they regard it as a major obligation of every Shiah Muslim. It was instituted by God as a token of regard for the Prophet and his family. (VII:1:41; XXXIII:27; LIX:6-9).
It is a 20% tax on all earnings after deduction of house-hold and commercial expenses.
Khums is paid to the mujtahid and is divided into two equal portions. One half of all receipts of khums by the mujtahid is the portion belonging to the Imaam in occultation and the mujtahid spends this portion in educational, social and economic projects for the betterment of the Shiah community. First priority is accorded to the community from which the khums was received. The second half is distributed amongst the poor and deserving descendants of the Prophet (the sayyids) each of whom may receive only up to a year's subsistence.