In macroeconomics, discretionary policy is an economic policy based on the ad hoc judgment of policymakers as opposed to policy set by predetermined rules. For instance, a central banker could make decisions on interest rates on a case-by-case basis instead of allowing a set rule, such as Friedman's k-percent rule, an inflation target following the Taylor rule, or a nominal income target to determine interest rates or the money supply. In practice, most policy actions are discretionary in nature.
"Discretionary policy" can refer to decision making in both monetary policy and fiscal policy. The opposite is a commitment policy.