What was name of the most important land tax upheld by feudalism under the king?
Scutage: Scutage is a medieval English tax levied on holders of a knight's fee under the feudal land tenure of knight-service. Scutage:  Under feudalism the king, through his vassals, provided land to knights for their support. Taxation in medieval England:  The most important tax of the late Anglo-Saxon period was the geld, a land tax first regularly collected in 1012 to pay for mercenaries.
geld