This report analyses twelve quality assurance systems that cover non-formal adult learning to identify the quality areas and criteria typically included in these systems, as well as the evidence that training providers can submit to prove compliance with them. The different quality areas, criteria and indicators are analysed and structured in the report using the four phases of the European Quality Assurance Reference Framework for Vocational Education and Training (EQAVET): planning, implementation, evaluation and review. The review finds that, given their direct impact on training provision, the most common indicators in the systems reviewed refer to the design of the training programme (planning phase) and to the staff working at the training provider (implementation phase). In addition, the quality assurance systems analysed generally require gathering feedback from relevant actors involved in the training process, such as trainers and trainees (evaluation phase), and to develop an improvement plan (review phase). The goal of this analysis is to support institutions from countries not covered in the report in developing new quality assurance frameworks by providing guidance on the most relevant areas for non-formal learning quality assurance, as well as examples of how to define the systems' indicators.