The computational complexity of seriatim actuarial projections forces life insurance companies to compress their portfolio of liabilities to a set of representative model points. Since such projections are inevitable in order to meet regulatory requirements, portfolio compression is widely carried out in practice. We present a comprehensive and well-structured process detailing each step and providing an extensive overview over the corresponding literature. We further embed the process in a straightforward mathematical framework. Thereby, the formulation of compression as an optimization problem paves the way for assessing the compression quality. In order to express compression quality with respect to several dimensions in a single figure, we define general requirements towards a validation function. Moreover, we set up a specific function in line with these requirements and the theory of multiple criteria decision making (MCDM) and focus on sound methods for calibrating the validation function’s parameters.