The impact of the Bulgarian pension sys­tem reform, implemented with the 2015 Social Insurance Code amendment act, on the im­plicit pension debt is the main focus of the present article. Holzmann’s methodology for calculation of open group pension liabilities is used (Holzmann et al., 2004). The long term forecasting of public pension fund revenues and expenditures is made possible through Professor John Wilkin’s actuarial model, which has been prepared within the scope of the World Bank’s assistance for Bulgaria in the implementation of the pension reform. The in­put in the model consists of demographic and macroeconomic suggestions as well as social security data for the 40-year period (2015- 2055) after pension reform enactment. The impact of the pension reform’s parameters on the implicit pension debt of the Bulgarian public pension system is elaborated through scenario analysis. Among the key findings of this article are the important role of the in­creasing of retirement age and serving period, as well as the contribution size for pension, for decreasing of implicit pension debt.