Is it permissible for a government employee to take his salary through an overdraft from the bank in the event that the salary has not been deposited?

If the amount they pay the borrower is less than what they take from him, then that is unlawful because it is usury (riba). However, if what is taken from his salary is equivalent to what was previously paid to him, then there is no harm, and this is called a goodly loan (qard hasan).