Is it permissible for an employee to sell the voucher equivalent to the value of the coat provided by the governmental department, especially since some sell it for less than its value, and does this fall under what is called "waiver of benefit"?

The vouchers issued by some institutions to employees as gifts or rewards represent offers, not cash. Selling them before taking possession is a matter of dispute among jurists. The majority do not permit this due to lack of ownership, while the Malikis and some other scholars deem it permissible, as they consider possession a condition of completion, not a condition of validity. The preponderant opinion is the permissibility of selling a gift before taking possession of it. Therefore, there is no harm in selling these vouchers.