Rapid population ageing and the influx of baby boomers arriving at the age of retirement is generating a considerable threat for the financial sustainability of Belgium’s old-age pension system. Additionally, the country must cope with relatively low elderly employment rates and one of the earliest average effective retirement ages in the OECD. Concurrently to a trend observed in many developed countries, Belgium has witnessed an upward trend in male employment rates starting in the 2000’s and a long-term structural increase in female employment. While these tendencies in employment show potential for improving the financial sustainability of the pension system, they are in no way sufficient to absorb the overwhelming burden of population ageing on public old age spending. Confronted with these demographic trends, the Belgian government has implemented various social security reforms since the 1990’s to safeguard the financial sustainability of the pension system. These reforms were mainly aimed at tightening access to early labor force exit pathways and at reducing the incentives of early old-age pension benefits claiming. The objective of the thesis is to explore the impact of the social security system as a driver of retirement, using Belgium as a case study. We use detailed social security eligibility and benefit calculation rules and their reforms from the 1980's until today to compute measures of financial retirement incentives and we study their impact on the retirement probability of older Belgian workers.