Theory suggests that government should as far as possible smooth taxes and its recurrent consumption spending, which means that government debt should act as a shock absorber, and any planned adjustments in debt should be gradual. This suggests that operational targets for governments (e.g. for 5 years ahead) should involve deficits rather than debt, because such rules will be more robust to shocks. Beyond that, fiscal rules need to reflect the constraints on monetary policy, and the extent to which governments are subject to deficit bias. Fiscal rules for countries in a monetary union or fixed exchange rate regime need to include a strong countercyclical element. Fiscal rules should also contain a ‘knock out’ if interest rates hit the zero lower bound: in that case the fiscal and monetary authorities should cooperate to formulate a fiscal expansion package that allows interest rates to rise above this bound. In more normal times, the design of fiscal policy rules is likely to depend on the extent to which governments are subject to deficit bias, and the effectiveness of any national fiscal council. For example, governments that had not shown a history of deficit bias could aim to target deficits five years ahead (rolling targets), and these would not require cyclical adjustment. In contrast, governments that were more prone to bias could target a cyclically adjusted deficit at the end of their expected period of office. In both cases fiscal councils would have an important role to play, in ensuring plans were implemented in the first case and allowing for departures from target when external shocks occurred in the second.