The country's inability to pay it's debt or reach a deal makes it the largest nation in history to be in arrears to the IMF.
What happens now?
Greece’s missed payment to the IMF is a milestone—it’s both the first time a developed country has missed such a payment, and the first time a Eurozone country has defaulted on its debt. (Or it’s “in arrears”—as Bouree Lam explains below, the IMF isn’t using consistent terminology.)
But that doesn’t mean automatic expulsion from the Eurozone. Yanis Varoufakis, the country’s finance minister, made the case on his blog three years ago that “a defaulted Greece can easily remain in the Eurozone,” and that in fact “Europe’s optimal strategy is to let Greece default.” The Lisbon Treaty, which forms the legal basis of the European Union, actually makes no provision for a member’s expulsion. A 2009 legal analysis by the ECB found that, “while perhaps feasible through indirect means, a Member State’s expulsion from the EU or EMU [the European Monetary Union], would be legally next to impossible.”