From a fascinating story at The Wall Street Journal:
The fastest-growing asset on bank balance sheets this year is cash. Since the beginning of the year, U.S. bank holdings of cash are up 83%, or $890 billion, to $1.98 trillion. ...
BNY Mellon said that customers that have deposited more than $50 million into their accounts since the end of July will face an annual fee of at least 0.13% of the excess deposits. ...
Holding cash comes at a cost to banks. Bank of New York and others pay fees of about 0.10% to the FDIC to insure their deposits, said people familiar with the matter. ...
One place banks have turned to put their cash is the Federal Reserve. Since late 2008 it has been paying 0.25% interest on funds banks hold ... in reserve with the Fed.
Learn all about it, here.