This paper revisits fiscal sustainability conditions by relaxing the long-run time-invariance restriction on the parameters commonly imposed in the existing literature. For this purpose, we propose to extend the stock-flow econometric analysis, which bridge the use of government's intertemporal budget constraint as well as a government's fiscal manoeuvre, by allowing time-varying multicointegration. We applied the procedure to the Portuguese case. We found that fiscal practice has taken various directions in this country since the end of the 90s, involving different situations regarding fiscal sustainability.