What was the Inca tax paid in labor called?

The Inca tax paid in labor was called mit'a. It was a mandatory public-service obligation in which subjects contributed work rather than money or goods to the state.

Mit'a labor supported the empire’s infrastructure and administration. Communities supplied workers for roads, bridges, agricultural terraces, fortifications, storehouses, mines, farming, and military service. The work was organized in rotating turns, allowing households to meet their own agricultural needs as well.

The word comes from Quechua and conveys the idea of a turn or season. Mit'a should not be confused with ayni, a system of reciprocal help between individuals or households, or mink'a, a form of communal labor. Spanish colonial authorities later adapted the mit'a system, especially for silver mining at Potosí, where it became far more coercive and destructive than its original Inca form.