Is it Islamically permissible for an installment sale contract to stipulate the confiscation of the entire down payment and installments paid, in addition to the company's right to calculate 15% of the total contract value as compensation in the event of the buyer's breach or withdrawal from the purchase?

A penalty clause is permissible in financial contracts, except for those where the primary obligation is a debt, such as contracting and supply agreements. It is not permissible in installment sales if the debtor delays payment. The actual financial damage must be the basis for compensation, and it is not enforceable if the breach is beyond one's will or if no damage occurred. If the penalty clause is exaggerated, it should be referred to justice and fairness in assessing the damage. It is not permissible for the company to confiscate all paid installments upon termination of the contract due to late payment, as this is deception (gharar) and injustice, even if the termination of the contract itself is permissible.