The latest dust-up in the battle for NYSE Euronext has centred on potential cost savings from a deal. Investors, though, may want to focus on the tax implications of the competing proposals.

NYSE said it had identified €100m in additional synergies likely from its proposed $10bn-or-so merger with Germany's Deutsche Börse. NYSE doubtless hopes the latest figure, on top of an initial synergy estimate of €300m, will make its deal look more attractive versus a competing $11bn offer from Nasdaq and IntercontinentalExchange. The Nasdaq side, whose offer has been twice rejected by NYSE, quickly questioned the new estimate.