The stabilising expenditure rule (SER) imposed on general government (GG) sector in Poland has been binding since 2014. According to this rule, about 90% of GG expenditure will grow in line with the real medium-term GDP, or slower if there is excessive debt or deficit, or balance does not meet the medium-term objective. It was shown in this paper how the SER affects the most important public finance indicators in the period 2014-2040. The consequences of the lowered debt thresholds in the SER's correction mechanism due to the pension reform were also presented. Finally, future fiscal policy conducted under the new rule was simulated and assessed.