The use of ashes from biomass combustion and biochar as fertilizers or soil improvers is gaining increasing attention in the context of a circular economy and sustainable agriculture. Biomass ash contains macronutrients (e.g., potassium, phosphorus, and calcium) and can increase soil pH, while biochar has high stability in soil and the ability to sequester carbon, helping to improve soil fertility and water retention. Despite these benefits, it is crucial that an appropriate legal framework and quality standards are in place to ensure the safe and effective use of these materials. Efforts have been made both internationally and in the European Union to regulate the status of biomass ash and biochar—from legal classification, to quality requirements, to their inclusion in the official fertilizer cycle (Silva et al. in J. Clean. Prod. 214:112–124, 2019 [1]; Jarosz-Krzemińska and Poluszyńska in Energies 13(18):4805, 2020 [2]). This chapter presents the current regulation of biomass ash and biochar-based fertilizers, discusses quality and safety standards for these products, and examines future agricultural policy perspectives in this area.