Actuaries working on valuations of social security arrangements often face problems with the availability and quality of suitable data.  Such problems can be particularly acute for actuaries working on valuations on a consultancy basis as opposed to as permanent employees of an arrangement. This paper sets out considerations in specifying and validating the data required for the valuation of a typical social security arrangement, and presents processes for checking the quality of the data. It also gives a data template that may be a useful guide. It may be useful for actuaries to share this paper with their social security arrangement colleagues and clients to help all parties in understanding what kind of data are needed and why.