This paper develops a stylized budgeting framework to analyze the effects of macroeconomic shocks and government bond market conditions on public finances. We focus on the impacts of primary fiscal balance shocks, growth, and interest rate shocks on budgetary sustainability. We consider the effects of financial sector bailouts, uncertainty about aging costs and instability viz. speculation in government bond markets. The framework is applied to the case of Belgium, where recently these issues have played an important role. A scenario analysis of budgetary adjustment under alternative hypotheses is carried out to analyze Belgian fiscal sustainability over the next 20 years.