Monetary circuit theory is a heterodox theory of monetary economics, particularly money creation, often associated with the post-Keynesian school. It holds that money is created endogenously by the banking sector, rather than exogenously by central bank lending; it is a theory of endogenous money. It is also called circuitism and the circulation approach.
The key distinction from mainstream economic theories of money creation is that circuitism holds that money is created endogenously by the banking sector, rather than exogenously by the government through central bank lending: that is, the economy creates money itself (endogenously), rather than money being provided by some outside agent (exogenously).
These theoretical differences lead to a number of different consequences and policy prescriptions; circuitism rejects, among other things, the money multiplier based on reserve requirements, arguing that money is created by banks lending, which only then pulls in reserves from the central bank, rather than by re-lending money pushed in by the central bank. The money multiplier arises instead from capital adequacy ratios, i.e. the ratio of its capital to its risk-weighted assets.
Circuitism is easily understood in terms of familiar bank accounts and debit card or credit card transactions: bank deposits are just an entry in a bank account book (not specie – bills and coins), and a purchase subtracts money from the buyer's account with the bank, and adds it to the seller's account with the bank.
As with other monetary theories, circuitism distinguishes between hard money – money that is exchangeable at a given rate for some commodity, such as gold – and credit money. The theory considers credit money created by commercial banks as primary (at least in modern economies), rather than derived from central bank money – credit money drives the monetary system. While it does not claim that all money is credit money – historically money has often been a commodity, or exchangeable for such – basic models begin by only considering credit money, adding other types of money later.