All Economic Regulations are Transparent Act of 2021 or the ALERT Act of 2021 This bill establishes various reporting requirements with respect to federal agency rulemaking. Specifically, each agency must submit a monthly report to the Office of Information and Regulatory Affairs (OIRA) for each rule the agency expects to propose or finalize during the following year, including information about the objectives and legal basis for the rule as well as whether the rule is subject to periodic review based on its significant economic impact. Additionally, each agency must submit a monthly report for any rule expected to be finalized during the following year for which the agency has issued a general notice of proposed rulemaking, including an approximate schedule for completing action on the rule and an estimate of its cost and economic effects. OIRA must publish this information online and, subject to certain exceptions, a rule may not take effect until the information has been published for at least six months. The bill also requires OIRA to annually publish in the Federal Register specified information it receives from agencies under this bill, including a list of each rule an agency has proposed and the total cost of all rules proposed or finalized. OIRA must further publish online (1) any analysis of the costs or benefits of rules that were proposed or finalized during the previous year, and (2) a list of rules that were subjected to various forms of review during the previous year.