Banks borrow short and lend long. Meaning they take short-term deposits (e.g. current account balances) and make long-term loans (e.g. mortgages). They normall

Banks borrow short and lend long. Meaning they take short-term deposits (e.g. current account balances) and make long-term loans (e.g. mortgages). They normally make a profit, because they borrow short paying low rates, and lend long receiving high rates. Easy. Head to the golf course. If the yield curve inverts, banks lose money ... their capital ratios and share prices fall ... they become more risky and less creditworthy ... people withdraw their money ... bank runs, ATMs stop working, bail-ins ... your current account is permanently unavailable (see Cyprus, Greece). Note that many banks, especially European banks, are starting from an existing almost-bankrupt state, with plummeting share prices (DB, UniCredit, BBVA, BNP). If the EUR yield curve inverts, they all crash faster than an anvil without a parachute (DB is already giving the anvil a good race).