What is the ruling on financial penalties imposed on retirement funds for late payment, and is retirement money lawful?

It seems that "installments" refers to the employee's monthly contributions to the pension fund. If he delays payment, he pays more than what was originally stipulated. If the fund is a cooperative solidarity fund, there is no harm in this, as long as it is done according to the agreement among the subscribers. It is as if the subscriber committed himself to donate more than the known installment in case of delay, and whoever obligates himself to a good deed is bound by it. However, if the fund is commercial and the transaction is an exchange, then it is not permissible to subscribe to it, and the fines would be an increase in sin.