What is the difference between stipulating an additional amount or an additional percentage on the sale price in exchange for an extension in the payment period, if both are regulated by a contract acceptable to both parties?

It is permissible to sell a commodity for more than its current price due to deferred payment, and this is the view of the majority of jurists. The difference between specifying a monetary amount and a percentage in Mudarabah (profit-sharing) is that specifying a percentage guarantees the Mudarib (investor) a share of the profit, whether small or large, whereas specifying an amount may not be realized, or it may deprive the other partner of profit, or it may be detrimental if the profit exceeds the specified amount. The fundamental principle is that Mudarabah is a partnership in profit, and justice dictates that the profit should be a shared portion.