Cosmetic Supply Chain Transparency Act of 2021 This bill requires the Food and Drug Administration (FDA) to maintain a list of certain nonfunctional constituents in cosmetics that are harmful to human health or the environment, authorizes the FDA to request from a brand owner (i.e., the entity bringing a cosmetic to market) certain information about a cosmetic's ingredients, and addresses related issues. For each listed nonfunctional constituent, the list must identify the ingredient or cosmetic (or category of ingredient or cosmetic) in which the constituent is known or reasonably expected to be present. The FDA must also (1) establish procedures for petitions to add substances to the list, (2) issue guidance for industry related to testing and detecting such nonfunctional constituents, and (3) establish a committee to provide advice on creating the list and developing the required industry guidance. Within a year of a nonfunctional constituent being added to the list, a supplier of an ingredient or cosmetic must test for that constituent and provide a brand owner the results and other information before selling the ingredient or cosmetic to the brand owner. A supplier of an ingredient or cosmetic must provide additional information about the item upon a brand owner's request. Brand owners must maintain records with information about the suppliers of ingredients and raw materials used in their cosmetics and provide such information to the FDA upon request. The bill also imposes civil penalties for brand owners and suppliers that violate this bill's provisions.