Is dealing with an installment company that issues a card to the customer, through which goods can be purchased from contracted stores, with the store receiving a percentage from the company, considered a prohibited transaction?

The transaction between the company and the cardholder is a loan with an increment, which is usury (riba) and impermissible; it is not an installment sale. Therefore, it is not permissible to cooperate with this company. Any commission paid from this transaction is forbidden, as it is either part of the usurious interest or compensation for cooperation in a forbidden contract. These funds must be disposed of by spending them on Muslim welfare projects or giving them to the poor and needy. Cooperation with the company must cease in the future, unless the transaction is adjusted to comply with Sharia guidelines, such as the company first purchasing the item and then selling it on installment. This is in accordance with the Almighty's saying: "And cooperate in righteousness and piety, but do not cooperate in sin and aggression."