The contract is meant to follow up to on previous project “Nanomaterial Risk Assessment: A regulatory way forward for sameness and grouping approaches” contracted in 2023. In the previous contract, a framework was developed to assess the acceptable variation within each characteriser of a Nanoform. That project aimed at exploring ways to simplify nanoforms registration process and, ultimately, its’ associated testing burden. As an outcome, a series of binary decision trees and respective variability threshold were produced, covering each mandatory characteriser. The framework was developed based on a limited set of information covering metallic and carbon-based nanomaterials. The present contract aims at refining the threshold values pre-established and validating it with additional data sets, covering a wider range of chemical types. This project’s outcome is expected to become a basis for ECHA to develop new guidance for registrants of nanoforms of a substance.