Royal fifth

The royal fifth (Spanish and Portuguese: quinto real / quinto del rey) is a historical royal tax which reserves to the monarch 20% of all precious metals and other commodities (including slaves) acquired by his subjects as war loot, found as treasure or extracted by mining. The 'royal fifth' was first instituted in medieval Muslim states from interpretations of Qur'an, though the extent to which it applied was debated between schools of Islam. During the Age of Exploration, Christian Iberian kingdoms and their overseas colonial empires also instituted the tax, though to encourage exploration, some monarchs allowed colonists to keep some or all of the fifth.