Is it permissible for the company to impose a fine for late payment of apartment installments, knowing that the sales contract stipulates a 3% fine, and that the company had not applied it previously but began to demand it after incurring losses?

Imposing a financial penalty on a buyer who is late in paying loan installments is a usurious and forbidden condition. It is not permissible to enter into a contract that includes it. Working to collect this forbidden penalty is not permissible, and it is not permissible for the questioner to undertake this work unless there is a religious necessity that permits the commission of what is otherwise forbidden.