Return will be voluntary and flexible.
Investigation into accounting errors by PwC also found 2018 half-year reported profit was adjusted by about $8.3 million.
Move follows J Walter Thompson and Wunderman merger in 2018.
Havas is expected to repitch.
Work that promises to improve the world but doesn't take real action is 'infecting' the industry, Unilever CEO says.
Sale of Droga5 to Accenture will help it stay relevant, founder says.
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