Dentsu has been formally charged over illegal overtime practices following the death of an employee in 2015.
Matsuri Takahashi had been working at the Japanese firm for less than a year but is reported to have worked 100 hours of overtime a month leading up to her death, sometimes only sleeping 10 hours a week.
The company’s Tokyo headquarters were subsequently raided by the Tokyo Labor Bureau after the government launched an investigation into the 24-year-old’s death.
Less than three months later the advertising group’s chief executive Tadashi Ishii stepped down, saying he wanted “take responsibility as a manager for failing to fix the company’s notoriously punishing culture of overtime work.”
Local daily newspaper, The Asahi Shimbun, reports that Tokyo District Public Prosecutors Office is seeking a fine against the company.
Several Dentsu managers had also been investigated but will not face individual charges on the grounds that their actions were not malicious enough to merit punishment.