In a fractional reserve banking system, as is the case in the euro area and other modern  BIS central bankers’ speeches  1  economies, the bulk of the money stock takes the form of bank deposits. Money is the liability of the banking system as a whole, and it circulates electronically.
For money to be “single”, then, the payments system has to work smoothly across the jurisdiction – that is actually one of our statutory tasks – and the banking system that creates money has to be sound.