There are differences in the interpretation and scope of zakat and other related taxes in various sects of Islam. For example, "khums" is interpreted differently by Sunnis and Shi'ites, with Shia expected to pay one fifth of their excess income after expenses as "khums", and Sunni don't. At least a tenth part of zakat and "khums" every year, among Shi'ites, after its collection by Imam and his religious deputies under its doctrine of "niyaba", goes as income for its hierarchical system of Shia clergy. Among Ismaili sub-sect of Shias, the mandatory taxes which includes zakat, is called "dasond", and 20% of the collected amount is set aside as income for the Imams. Some branches of Shia Islam treat the right to lead as Imam and right to receive 20% of collected zakat and other alms as a hereditary right of its clergy.