Finalization Day was July 14, 2015. In Vienna, Iran and six powers (the United States, Russia, China, France, Britain and Germany, known together as the P5+1) wrapped up negotiations on the JCPOA, with the European Union’s High Representative leading the diplomatic effort. The Arms Control Association records that the UN Security Council endorsed the deal on July 20, 2015, in Resolution 2231.
The timeline written into the deal
The JCPOA ran on a schedule of named days. Adoption Day, October 18, 2015, started the work of putting the commitments into practice. Implementation Day followed on January 16, 2016, once the IAEA confirmed that Iran had made the central cuts to its program and accepted tighter monitoring. That finding set off sanctions relief from the UN, the EU and the US. Transition Day, set for October 18, 2023, was meant to bring the lifting of missile restrictions and the remaining EU nuclear sanctions. Termination Day, October 18, 2025, would close the Security Council’s file on Iran’s nuclear program.
The EU’s foreign service describes the package as a main text with five technical annexes, covering nuclear measures, sanctions, civil nuclear cooperation, the Joint Commission and the implementation plan.
What Iran gave up
The limits were specific. For a decade, the number of working centrifuges was to be cut to 5,060 of the IR-1 type, within a total of 6,104, and the surplus above 13,000 machines was to be dismantled and stored under IAEA watch. For 15 years, enrichment could not rise above 3.67 percent. Holdings of uranium at that level had to stay below 300 kilograms over the same stretch. Anything beyond that was to be sold, sent abroad or diluted.
At Arak, the original reactor core was to be removed and disabled, then replaced with one that yields less weapons-grade plutonium. The EEAS adds that Fordow was to be repurposed so it could not produce highly enriched uranium. By the EU’s estimate, the package pushed Iran’s breakout time out from roughly 2 months to at least 1 year.
Inspection and enforcement
The IAEA carried the verification burden. Uranium mines and mills were to be monitored continuously for 25 years, and centrifuge production facilities for 20. Iran also committed to implement, and eventually ratify, an additional protocol to its safeguards agreement. A Joint Commission of the P5+1, the EU and Iran, eight voting members in all, was to meet quarterly for 25 years and oversee the deal.
Sanctions came back through a mechanism known as snapback, a veto-proof route for any party to restore earlier UN measures in case of noncompliance.
How it came apart
The United States announced its withdrawal on 8 May 2018, according to the EEAS. Iran began reducing its commitments in July 2019. Talks in Vienna to bring Washington back ran from April 2021 until September 2024 without an agreement. On 28 August 2025, the three European parties, France, Germany and Britain, told the Security Council that Iran had significantly failed to perform and invoked snapback. The 30-day window closed without an extension. On 28 September 2025 the Council restored every UN nuclear sanction that Resolution 2231 had terminated. That was three weeks before the date the agreement itself had set for its end.
Sources
- The Joint Comprehensive Plan of Action (JCPOA) at a Glance (Arms Control Association)
- NUCLEAR AGREEMENT – JCPOA (EEAS)
