A more thorough explanation:

Term: Droit de quint
Definition: In medieval France, the droit de quint was a payment made by a noble vassal to the king every time the vassal's fief changed ownership. This payment was equal to one-fifth of the value of the fief. Example: If a noble vassal sold his fief to another noble, he would have to pay the king one-fifth of the value of the fief as the droit de quint. For instance, if the fief was worth 1000 francs, the noble vassal would have to pay the king 200 francs as the droit de quint. The example illustrates how the droit de quint worked in medieval France. It shows that the payment was made every time the ownership of the fief changed, and it was based on the value of the fief. The payment was a way for the king to maintain his authority over the nobles and to ensure that he received a share of the wealth generated by the fiefs.