Are the transactions related to the illness fund, which deducts a fixed monthly amount from a worker's salary for the purpose of reimbursing varying percentages of medication and treatment expenses, permissible or forbidden?

It is permissible to subscribe to a Takaful (Islamic cooperative) retirement fund that provides health insurance services for the employee, as well as if it invests the employees' funds in permissible ways according to the regulations of legitimate Mudarabah (profit-sharing partnership) to spend a portion of it on treatment after retirement. However, if the fund invests in usury (riba) and unlawful activities, it is not permissible to subscribe to it voluntarily. For someone who is forced into it, they may benefit from what was deducted from their salary, and they should dispose of any excess by spending it on the welfare of Muslims and the poor.