The consumption of fish has lately seen an upward trend and with it, the issue of adulteration of fish with unapproved chemicals and additives has also come into the light. Formalin (formaldehyde in water) is a common adulterant in fish. Traders and suppliers use it to extend the storage life of fresh or chilled fish and artificially improve the sensory attributes. The FSSAI Referral Laboratory on fish and fish products, Central Institute of Fisheries Technology (CIFT)- Kochi, has reported the presence of residues of these chemicals in freshly marketed fish, inter-state fish consignments and even in ice used during transportation. Although, the amount of formalin in fish decreases overtime during storage but cannot be removed completely. Consumption of fish adulterated with formalin can cause health conditions such as abdominal discomfort, vomiting, renal injury, etc. This guidance note has been prepared jointly by FSSAI and ICAR-CIFT to guide consumers, traders and food testing laboratories on the best practices to avoid, restrict and detect formalin adulteration in fish, respectively.