Catastrophic Risk Transfer Act of 2021 or the CART Act This bill establishes a system for the taxation of catastrophic risk transfer companies and their security holders to ensure sufficient capital to cover catastrophic insurance losses. The bill defines catastrophic risk as a risk of loss that has a low likelihood of occurring but that would be large in amount. The bill defines catastrophic risk transfer company as any domestic corporation created and regulated under state law with the purpose of entering into one or more insurance or reinsurance agreements covering catastrophic risk.