head or poll tax that early Islamic rulers demanded from their non-Muslim subjects.

Islamic law made a distinction between two categories of non-Muslim subjects—pagans and dhimmis (“protected peoples,” or “peoples of the book”; i.e., those peoples who based their religious beliefs on sacred texts, such as Christians, Jews, and Zoroastrians). The Muslim rulers tolerated the dhimmis and allowed them to practice their religion. In return for protection and as a mark of their submission, the dhimmis were required to pay a special poll tax known as the jizya. The rate of taxation and methods of collection varied greatly from province to province and were greatly influenced by local pre-Islamic customs. In theory the tax money was to be used for charitable purposes and the payment of salaries and pensions. In practice, however, the revenues derived from the jizya were deposited in the private treasuries of the rulers. The Ottomans usually used the proceeds of the jizya to pay their military expenses.

A convert to Islam was, in theory, no longer required to pay the jizya. The Umayyad caliphs (661–750), however, faced with increasing financial difficulties, demanded the jizya from recent converts to Islam as well as from the dhimmis. This discrimination against converts was a cause of the Abū Muslim rebellion (747) in Khorāsān and helped to precipitate the downfall of the Umayyads.