The Vodafone Group has served a 'dispute notice' on the Centre, the first step before it begins international arbitration proceedings under the India-Netherlands bilateral investment treaty against the government's controversial move to tax the company's acquisition of Hutchison Essar in 2007. This is the first formal action initiated by the world's largest mobile operator since the government included a proposal in last month's budget to tax overseas transactions involving sale of Indian assets on a retrospective basis.