This technical guide explains the methodology and process flow of ILO/PENSIONS and serves as a reference manual for users. ILO/PENSIONS is part of a series of quantitative tools developed by the Social Protection Department to support evidence-based policy reforms. The related technical guides and models can be made available to experts in ILO constituent countries as part of ongoing technical support and capacity-building activities in quantitative techniques in social security. Users of ILO/PENSIONS are expected to be qualified quantitative experts in the actuarial field who have substantial experience in the design and costing of social protection systems. The ILO/PENSIONS model and technical manual can also be used as a teaching aid for specific training in social security quantitative techniques.