In (web-based) collaborative learning, practitioners increasingly stress the need to acknowledge individual efforts. To this end, peer assessment is regarded as a valuable tool. Research, however, shows shortcomings in the calculations and flexibility of peer assessment formats that are used to transform a group score into individual scores. This chapter proposes an innovative approach by presenting peer assessment formats that underlie sound formulas, but moreover allow flexibility in peer assessment design. Subsequently, the effects of the formats on individual scores are investigated. The results reveal that our formulas and formats outweigh ‘traditional’ practices to utilise peer assessment for transforming a group score into individual scores. Guidelines for practitioners on the application of peer assessment formats are presented, as well as an outline for a research agenda with a strong focus on the development of flexible peer assessment in (web-based) collaborative based learning.