Unfunded Mandates Accountability and Transparency Act This bill revises rulemaking requirements with respect to unfunded mandates. Specifically, the bill requires federal agencies to prepare and publish in the Federal Register an initial and final regulatory impact analysis prior to promulgating any proposed or final major rule. The analysis must include regulatory alternatives to the rule. Major rule means a rule that the Office of Information and Regulatory Affairs determines is likely to cause an annual effect on the economy of $100 million or more; a major increase in costs or prices for consumers, individual industries, federal, state, local, or tribal government agencies, or geographic regions; or significant adverse effects on competition, employment, investment, productivity, innovation, public health and safety, or the ability of U.S.-based enterprises to compete with foreign-based enterprises in domestic and export markets. Before promulgating any proposed or final major rule, an agency shall select the regulatory alternative that maximizes net benefits, taking into consideration only the costs and benefits that arise within the scope of the statutory provision that authorizes the rulemaking, with exceptions. The bill prohibits Congress from considering a bill that increases private sector costs more than a certain amount unless certain conditions are met.