When the Federal Reserve (Fed) expanded its balance sheet via quantitative easing (QE), commercial banks financed reserve holdings with deposits and reduced their average maturity. They also issued lines of credit to corporations. However, when the Fed halted its balance-sheet expansion in 2014 and even reversed it during quantitative tightening (QT) starting in 2017, there was no commensurate shrinkage of these claims on liquidity. Consequently, the financial sector was left more sensitive to potential liquidity shocks, with weaker-capitalized banks most exposed. This necessitated Fed liquidity provision in September 2019 and again in March 2020. Liquidity risk-exposed banks suffered the most drawdowns and the largest stock price declines at the onset of the Covid crisis in March 2020. The evidence suggests that the expansion and shrinkage of central bank balance sheets involves tradeoffs between monetary policy and financial stability.