Since the great financial crash, the need for new fiscal rules to prevent unsustainable fiscal policies is universally recognised. In practice such rules, including those in the Stability and Growth Pact, have proved to be impossible to enforce. Thus, to avoid unsustainable fiscal policies reappearing, and to prevent monetary policy from being undermined by undisciplined governments, there is a need for a framework capable of imposing fiscal discipline. This paper considers an intertemporal assignment, where fiscal policy focuses on long-term objectives and monetary policy on short-term stabilisation. We argue for public sector debt targets as a practical way to achieve such a set up, and an excess debt protocol is constructed to give enforceable form to those targets. The ideas of “fiscal space” and optimal debt levels are used to provide a mechanism for identifying a stable region within which the debt targeting regime should operate. Making these factors explicit would both improve the credibility of planned fiscal policies and reduce risk premia on borrowing costs. We finally show how Europe’s competitiveness pact, and debt restructuring operations, can be used to maximise the available fiscal space.