Governors of provinces that were required to submit a land tax quota would use rice collected from koden as a financial resource in order to purchase silk or iron based on koka (selling prices) and sent it to the Daijokan chuke (manager of the kitchen of the Great Council of State) in the central government.
地子の割当を受けた令制国では、公田から賃租された地子稲を財源として沽価に基づいて絹や鉄などを調達して中央の太政官厨家に送付した。