Iran Nuclear Verification Act This bill prohibits the United States from becoming a party to the Joint Comprehensive Plan of Action (JCPOA) or any other agreement with Iran that relates to Iran's nuclear program until the President makes certain certifications. The JCPOA is an agreement, signed by Iran and several other world powers (including the United States), that places restrictions on Iran's nuclear program in exchange for certain sanctions relief. The United States withdrew from the JCPOA in 2018. The United States may not become a party to any such agreement until the President certifies to Congress that United Nations nuclear inspectors are allowed full access to all of Iran's nuclear facilities, and that they have completed their comprehensive report relating to those facilities.