The circular economy and the bioeconomy continue to grow. The goal is to reduce the dependence on fossil resources, GHG emissions and to increase recycling rates. Legal requirements like climate neutrality targets, recycling quotas, plastic taxes as well as consumer preferences, company commitments and stakeholder pressure are further driving the circular economy and bioeconomy. Along the complex supply chains, chain of custody concepts like mass balancing ensure the credible connection of sustainability information and the respective materials and products. Compliance with these concepts and its verification is crucial to ensure credibility for all companies involved and also for regulators. The presentation will explain how mass balance certification works, where it is applied, how certified value chains are developed and what type of claims can be made for final products. It will provide an overview on the ISCC PLUS system for the circular economy and bioeconomy, its sustainability, traceability and chain of custody requirements, ways to get certified under ISCC and benefits for ISCC certified companies.