Stock exchanges Deutsche Boerse and NYSE Euronext have formally asked EU regulators to begin a five-month anti-trust regulatory investigation into their merger plan.
The two exchanges agreed to merge in February to create a transatlantic operation that would be the world’s biggest equity trading platform by volume.
The European Commission has to decide whether the merger would be anticompetitive in Europe, where the combined entity would have a dominant presence in areas such as derivatives trading and clearing.
"Deutsche Boerse AG and NYSE Euronext confirm that they have today formally notified their planned business combination to the European Commission's Directorate-General for Competition," the exchanges said in a statement.
The EU regulators will hold a 25-day preliminary review, with room to extend it by up to ten days, in which the two companies can make undertakings such as propose divestments or concessions to ease the approval process.
If the regulator believes these are not enough and concerns over the merger remain, it can open an in-depth investigation lasting for up to 90 additional working days with the option to extend it for another 15 days.
EU competition commissioner Joaquin Almunia said in March he expected to take a long, hard look at the takeover, as it was a complex case.
He has also stressed the risks of a one-stop shop business model, saying he preferred an open system and interoperability.