Should one report an employee's negligence or remain silent to avoid causing his dismissal, knowing that he supports a family?

It is not permissible to abandon work duties or to be negligent in them, as this constitutes a breach of the agreed-upon conditions. Allah Almighty says: "O you who have believed, fulfill [all] contracts," and the Prophet, peace and blessings be upon him, said: "Muslims are bound by their conditions." Accordingly, the accountant's lack of competence and negligence justifies his dismissal, and it is permissible for you to work in his place. There is no blame upon you regarding the employer's decision to dismiss him or not. As for reporting him, if you are assigned to do so by the employer, then it is obligatory to fulfill that. If it is not your responsibility, then it is not necessary.