Banknotes, and currency, are a liability of the bank, and...

Banknotes, AND currency, are a liability of the bank, and an asset for the Treasury
A.k.a.  Seigniorage: The Honest Government's Guide to the Accounting of the Revenue from Money Creation
 by Marco Saba, July 21, 2016

"Federal Reserve notes, or currency, are a liability of the Federal Reserve." 
-  International Journal of Central Banking, March 2015

When a private central bank buy an asset by issuing money we have an appropriation of property by a private corporation using a sovereign right: money creation and disposing of the purchasing power thereof. This is why the bank has a liability from the issuance of currency into circulation: a liability toward the sovereign Treasury of the hosting nation where the currency was issued.

This liability – a private debt and a public credit – currently is unresolved because the central bank don’t pay it to the Treasury AND the Treasury fails to record a correspondent asset in his books. In this way we have a paradox of a private entity (the ECB or the Federal Reserve, as examples) that can buy the world issuing money without discharging her seigniorage debt to the Treasury. We have a false representation in the books of the bank as if the bank has discharged her debt to the public by recording an unresolved liability. It is the fault of the Treasury and of the government of the hosting nation not to spot this absurdity and to let the bank enrich herself at the expense of the public purse.

The correct way for accounting of FIAT money creation is to expose a liability for the central bank called CURRENCY IN CIRCULATION where you have to include banknotes AND electronic money. This liability must find a correspondent and equal asset in the Treasury books called SEIGNIORAGE RECEIVED FOR CURRENCY CREATION.

The example above can be adopted by analogy by any retail bank that do create electronic money by stealth as it is currently happening. The cash flow account of the bank must have a recording of an inflow each time new money is created.