Central banks manipulate their balance sheets to achieve their monetary policy and financial stability goals. Given the rising size of their balance sheets, central bank balance sheets are no longer independent of national and even global balance sheets. At the global level, flows and changes in stock must, like the game of sudoku, add up ex post, since excess consumption by one country are financed by surplus savings by other countries. At the same time, assets are by definition some other party’s liability. Using recently available net international investment positions, the chapter examines how reserve currency countries can run up large deficits in trade and capital account, so long as these are financed by the surplus countries. The study also shows that monetary policy by the reserve currency countries can facilitate capital account flows larger than trade flows, so that global imbalances could become exacerbated by central bank balance sheets.