IDB Transparency Act This bill directs the U.S. Executive Director at the Inter-American Development Bank (IDB) to act to reduce China's influence and to promote greater transparency about China's role in the IDB. Specifically, the U.S. Executive Director must vote and advocate to reduce the influence of China's government and Chinese companies at the IDB, including by opposing any IDB funding or projects that (1) are at least 10% funded by China or Chinese companies, and (2) present risks to U.S. national interests. Additionally, the U.S. Executive Director must vote against and take other actions to oppose the acquisition of IDB stock by China or Chinese companies. The bill also directs the Department of the Treasury to provide Congress with a report on China's influence at the IDB, including an action plan to reduce Chinese involvement in IDB projects. If the report is not provided within 180 days of the bill's enactment, the U.S. Executive Director must vote against or act to prevent a quorum for any vote related to the IDB budget until the IDB takes available steps to provide to Treasury the information needed for the report.