The underreporting of working hours is suspected to have occurred in several departments at advertising giant Dentsu Inc., which has already been referred to prosecutors on suspicion of violating the Labor Standards Law by having its employee work illegally long hours, according to sources.
Suspecting that underreporting of working hours has become a common practice at the company, the Health, Labor and Welfare Ministry intends to establish a case against the company on suspicion of having failed to make overtime payments as well, the sources said.
In November, ministry investigators raided Dentsu's headquarters and three branches and seized related documents.
After comparing the records of Dentsu employees' working hours and the times recorded under the entrance and exit control system, investigators found that employees in several departments stayed at their offices, despite records of their working time showing they had left the office.
It is thus highly likely that the employees reported their overtime hours as shorter than their actual overtime.
In the case of Matsuri Takahashi, who committed overwork-related suicide in December 2015 at the age of 24 while a first-year employee at Dentsu, records of her working hours showed she worked less overtime than the company's upper limit of 70 hours per month, set under a labour-management agreement.
However, labour authorities recognised that she did about 105 hours of overtime and her death was work-related.
The ministry referred Dentsu as a corporation and Takahashi's boss to prosecutors on suspicion of having her work illegally long hours, but is still continuing investigations regarding the underreporting of working hours.
For about 10 years through 2015, the company's headquarters and branch offices received corrective advisories five times from labour standards inspection offices over long overtime work, which exceeded the upper limit set by labour-management agreements.
The company therefore likely tried to keep recorded overtime hours below the upper limit, and this likely caused employees to underreport their overtime, the sources said.