"On July 14, 2015, Iran and the six powers that have negotiated with Iran about its nuclear program since 2006 (the United States, the United Kingdom, France, Russia, China, and Germany--collectively known as the P5+1) finalized a Joint Comprehensive Plan of Action (JCPOA). The JCPOA is intended to ensure that Iran's nuclear program can be used for purely peaceful purposes, in exchange for a broad lifting of U.S., European Union (EU), and United Nations (U.N.) sanctions on Iran. The JCPOA largely reflects what was agreed in an April 2, 2015, framework for the accord. The agreement replaces a Joint Plan of Action (JPA) interim nuclear accord in operation since January 2014. A resolution of disapproval of the JCPOA was not enacted by Congress by the deadline of September 17, 2015, set by the Iran Nuclear Agreement Review Act (P.L. 114-17). Iran's legislature approved the agreement and the JCPOA formally took effect on 'Adoption Day' (October 18, 2015), the date stipulated by the JCPOA as 90 days after passage of Resolution 2231 of July 20, 2015). On Adoption Day, the Administration issued provisional waivers for U.S. sanctions laws, which will take effect once Iran's compliance with initial required nuclear tasks is certified. That 'Implementation Day' was declared by the P5+1 on January 16, 2016, after the International Atomic Energy Agency (IAEA) certified that compliance. In the 114th Congress, some legislation has been introduced with the stated purpose of redressing asserted weaknesses of the deal."
CRS Report for Congress, R43333
Federation of American Scientists: http://www.fas.org/sgp/crs/index.html