The way I see it, any credit (including bilateral trade credit, overdrafts, and so on) adds to the monetary mass. Clearing houses and banks can act as underwriters for trade credit, and they can issue their own credit. Then the monetary authorities merge with banking supervision because they have a dual role as underwriters of bank credit and directors of monetary policy.

So, the State provides a deposit guarantee to the private banks in exchange for outsourcing to them the underwriting of trade credit and the creation of money as credit. The monetary authorities are supposed to keep track of the monetary mass created in this way, and curtail credit creation through their banking supervisory role if they see the monetary mass grow too much. If the monetary mass shrinks, the monetary authorities can inject money into the economy, by lowering interest rates or by buying bonds (issued by the State treasury or private firms) with newly created money.

Private banking for profit has an incentive to create as much credit as possible, as this results in higher personal income for the private bankers. This means that normally the central bank has to worry more about curtailing excessive private credit creation than about injecting money into the economy. But note that the conflict of interest inherent in private banking, where private bankers have an incentive to create as much credit as possible, whether the borrowers are creditworthy or not, in order to skim a fraction as personal profit, coupled with the identity of credit and money and the State guarantee of bank credit implicit in the explicit deposit guarantee, makes excessive private banking credit creation a form of counterfeiting.

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