United Nations Transparency, Accountability, and Reform Act of 2015

United Nations Transparency, Accountability, and Reform Act of 2015 Directs the President to use U.S. influence at the United Nations (U.N.) on a wide variety of issues, including to shift the funding mechanism for the regular budget of the U.N. from an assessed to a voluntary basis. Withholds up to 50% of nonvoluntary U.S. contributions to the regular budget of the U.N. unless the Department of State certifies to Congress that at least 80% of the total regular budget of the U.N. is apportioned on a voluntary basis. Requires the annual congressional budget justification to include a detailed itemized request in support of the U.S. contribution to the regular budget of the U.N. Sets forth requirements for the Department with respect to oversight of U.S. contributions to the U.N. and their use by U.N. entities. Prohibits the obligation or expenditure of a U.S. contribution to any U.N. entity unless the entity has provided the Department with a transparency certification and is in compliance with it. Prohibits the use of funds for: international organizations for any purpose other than an assessed U.S. contribution to a U.N. entity or other international organization; international organizations and programs for any purpose other than a voluntary U.S. contribution to a U.N. entity or other international organization; and international peacekeeping activities for any purpose other than a U.S. contribution to U.N. peacekeeping activities, to the International Criminal Tribunal for the former Yugoslavia, or to the International Criminal Tribunal for Rwanda. Directs the Department to withhold from the regular budget of the U.N. an amount equal to the amount of U.S. overpayments to the U.N. States that it is U.S. policy to oppose any proposals on expansion of the U.N. Security Council that would: (1) diminish U.S. influence on the Security Council, or (2) include veto rights for new Security Council members. Directs the President to use U.S. influence at the U.N. to: (1) initiate a comprehensive review of U.N. conventions on terrorism with the goal of making recommendations to the Security Council, and (2) ensure implementation of a directive with respect to anti-Semitic statements made at the U.N. or by its employees. Directs the Department to use U.S. influence at the U.N. to ensure: (1) Taiwan's participation in relevant U.N. entities, and (2) that no representative of a country designated as a Tier 3 country under the Trafficking Victims Protection Act of 2000 shall preside as chair or president of any U.N. entity. Directs the Department to withhold U.S. contributions from any U.N. entity that recognizes a Palestinian state or upgrades the status of the Palestinian observer mission at the U.N., the Palestine Liberation Organization, the Palestinian Authority, or any other Palestinian administrative organization or governing entity before achievement of a final peace agreement with Israel. Provides that until the Department makes a specified certification to Congress: (1) the Department shall withhold from a U.S. contribution to a regular budget of the U.N. an amount equal to the amount that would be allocated for the United Nations Human Rights Council (UNHRC), (2) the Department shall not make a voluntary contribution to UNHRC, and (3) the United States shall not run for a UNHRC seat. Directs the Secretary to withhold from a U.S. contribution to a regular budget of the U.N. an amount equal to the amount that would be allocated for: the U.N. Special Rapporteur on the situation of human rights in Palestinian territories occupied since 1967; and any other U.N. Special Procedures used to display bias against the United States or Israel or to provide support for any member state which is subject to Security Council sanctions, under a Security Council-mandated human rights investigation, has repeatedly supported acts of international terrorism, or is a country of particular concern for religious freedom or Tier 3 human trafficking. States that it is U.S. policy to oppose any legitimization of the Gaza report and to lead a diplomatic campaign supporting its revocation. Directs the Department to withhold from the U.S. contribution to the regular budget of the U.N. an amount that is equal to the percentage of such contribution that would be or has been expended by the U.N. for: (1) any part of the Gaza report process, and (2) any conference that advocated restrictions on free speech, religion, or other human rights and freedoms. Withholds U.S. contributions to the United Nations Relief and Works Agency for Palestine Refugees in the Near East (UNRWA) or to any successor or related entity unless the Secretary makes specified certifications to Congress. Expresses the sense of Congress with respect to UNRWA, including the withholding of U.S. contributions to UNRWA. Prohibits any U.S. contribution to the International Atomic Energy Agency (IAEA) from being used to support Technical Cooperation program assistance to North Korea and to any country that: (1) has repeatedly supported acts of international terrorism; or (2) is in breach of, or under investigation for breach of, obligations regarding its safeguards agreement with the IAEA, the Nuclear Non-Proliferation Treaty, or any relevant Security Council resolution. Directs the Department to withhold from the U.S. voluntary contribution to the IAEA an amount proportional to that spent by the IAEA on Technical Cooperation program assistance to such countries. Directs the President to use U.S. influence at the IAEA to block the Board of Governors membership of a state that has not signed, ratified, and implemented the Additional Protocol and is under investigation for a breach of, or noncompliance with, its IAEA obligations or principles of the Charter of the United Nations. Expresses the sense of Congress that U.S. national security interests are enhanced by the IAEA's Nuclear Security Action Plan and a resolution incorporating the Plan into the IAEA's regular budget should be adopted. Sets forth U.S. policy regarding reform of U.N. peacekeeping operations. Directs the President to use U.S. influence at the U.N. to oppose the creation of new, or expansion of existing, U.N. peacekeeping operations until the Department certifies to Congress that specified peacekeeping reforms have been adopted by the U.N. Department of Peacekeeping Operations or the General Assembly.