Chapter 26 Optimal fiscal and monetary policy We provide an introduction to optimal fiscal and monetary policy using the primal approach to optimal taxation. We use this approach to address how fiscal and monetary policy should be set over the long run and over the business cycle. We find four substantive lessons for policymaking: Capital income taxes should be high initially and then roughly zero; tax rates on labor and consumption should be roughly constant; state contingent taxes on assets should be used to provide insurance against adverse shocks; and monetary policy should be conducted so as to keep nominal interest rates close to zero. We begin by studying optimal taxation in a static context. We then develop a general framework to analyze optimal fiscal policy. Finally we analyze optimal monetary policy in three commonly used models of money: a cash credit economy a money in the utility function economy and a shopping time economy.