Is it permissible for a company that sells with permissible installment plans and Islamic Murabaha to deduct 15% from the remaining amount owed by the customer upon settlement of their account, knowing that the contract stipulates the agreed-upon amount?

It is not permissible to waive a portion of the debt for the customer in exchange for his prompt payment before the due date, according to the majority of scholars, unless the debt has already fallen due; in that case, there is no harm in waiving a part of it. However, if the debtor is in straitened circumstances, it is permissible to waive some of the debt for him when the due date arrives; indeed, it is commendable, due to the ease and relief it provides, as the Prophet, peace and blessings be upon him, said: "Whoever wishes Allah to save him from the distresses of the Day of Resurrection, let him relieve a person in straitened circumstances or waive a part of his debt."