There is a need for guidelines on validation of geotechnical finite element calculations. In Europe, different initiatives have started to work on this subject, among which the NAFEMS geotechnical committee. The author is a member of this committee and author of a reference publication on validation of numerical modelling in geotechnical engineering (Brinkgreve, 2013).This paper presents the main ideas of that publication. In addition to the reasoning behind validation of finite element calculations and a definition of related terms, it highlights the most important sources of discrepancies between a real project and its corresponding numerical model. The second part of the paper is devoted to the various methods of validation. The process of validation involves a validation of the model as a whole, as well as a validation of the various model components, but it starts with a verification of the methods and models implemented in the software. The last chapter describes some non-technical issues related with decisions, responsibilities and organizational issues to control the quality of numerical modelling as part of the geotechnical design process.