Kitab al-Kharaj (Book of Taxation)

كتاب الخراج

Written at the request of Caliph Harun ar-Rashid, this is the earliest surviving work on Islamic public finance and taxation. Abu Yusuf, the chief student of Abu Hanifah and the first Chief Justice of the Abbasid Caliphate, covers land tax, poll tax, trade regulations, public treasury, and the economic responsibilities of the state. It remains a primary source for Islamic economics and governance.