Serfs in the Middle Ages. Serfs in the middle ages were generally peasant farmers who provided manual labor in their master's land. The peasants would pay the lord some dues (in the form of labor) in exchange for using part of the lord's land to generate their own food.The serfs also had to pay taxes and fees. The Lord decided how much taxes they would pay from how much land the serf had, usually 1/3 of their value. They had to pay fees when they got married, had a baby, or there was a war. Money was not very common then, so usually they paid by giving food instead of money.