Jafari law departs from the Sunni schools in specific rulings beyond its distinctive sources. It permits mutah, a fixed term marriage contract for a specified duration and dower, a practice the Sunni schools hold to have been abrogated by the Prophet; it levies khums, a fifth of certain categories of income and profit, alongside the zakat charitable levy shared with Sunni practice, distributing khums traditionally between the Imam's representatives and the descendants of the Prophet; and its rules of inheritance and ritual purity diverge from Sunni practice at a number of points that shaped its own body of case law and commentary.
Because the twelfth Imam is held to remain in occultation rather than to have died, ordinary religious authority in Jafari practice rests not with a single successor but with the living community of qualified jurists, the marja al-taqlid, literally the source of emulation. A layperson selects a marja whose rulings, based on that jurist's own ijtihad, he or she follows on matters of law and practice, and a jurist's standing as marja rests on recognized scholarly seniority within the hawza seminary system rather than on appointment to an office. This structure, decentralized in principle even though a small number of senior marjas hold outsized influence in practice, is one of the clearest institutional differences between Jafari and Sunni religious authority.
Today the Jafari school is followed by the majority populations of Iran, Iraq, Bahrain and Azerbaijan, and by substantial minority communities in Lebanon, Kuwait, Pakistan, India and the Gulf states, tracing directly the geography of Twelver Shia Islam itself, of which it is the legal expression.
Sources An Introduction to Shi'i Islam: The History and Doctrines of Twelver Shi'ismMoojan Momen with The Most Learned of the Shia: The Institution of the MarjaiyyaLinda S. Walbridge (ed.)