Mahmud Yalavach was a Muslim administrator in the Mongol Empire who ruled over Turkestan as governor and eventually went on to be mayor of Taidu (today's Beijing). He was a Sogdiana Muslim Merchant who served as an administrator and advisor to Genghis Khan. Somewhere in the 1230s, he devised the census system accounting for the people in the newly formed Mongol Empire so they could be readily taxed. He went on to simplify the existing tax systems in his creation of two primary tax initiatives: The first was the poll tax known as qubchir, and the other was an agricultural tax known as qalan.