In 2006, the UN Security Council passed Resolution 1696  demanding that Iran suspend its enrichment activities. However, Iran failed to comply. Subsequently, the Council adopted Resolution 1737 that blocked Iran from trading nuclear materials and equipment.
In 2007, Resolution 1747 banned Iran’s arms exports froze assets and restricted travel of more individuals involved in nuclear activities.
In 2008, Resolution 1803 urged vigilance when dealing with Iranian banks. In 2010, Resolution 1929 imposed further restrictions on arms supplies, including tanks and helicopters, and added more individuals and entities to the sanctions list.
Trade between the US and Iran has been restricted since 1979. Since late 2008, US banks were prevented from processing so-called “U-turn transfers”  of money involving Iran. U-turn transfers are transactions involving the transfer of funds from a foreign bank that pass through a US financial institution and are then transferred to a second foreign bank.
In November 2011, further legislation threatened to cut off from the US financial system foreign financial institutions that conducted oil transactions with Iran’s central bank, and imposed penalties on countries that were not assessed as making adequate efforts to reduce their oil imports from Iran.
US imposed a new set of sanctions in February 2013 aimed at cutting off Iran’s access to oil revenues. Oil importers are required to pay into locked bank accounts that Iran can access only to purchase non-sanctioned goods or humanitarian supplies.
In 2011, the EU banned the export to Iran of key equipment and technology for the refining and production of natural gas.
In January 2012, foreign assets of the Central Bank of Iran that were held in financial institutions of the EU were frozen.
In March 2012, the Society for Worldwide Interbank Financial Telecommunication (SWIFT cut Iranian banks  from its system. This made it very difficult for money to flow in and out of Iran via official channels.
In July 2012, an EU ban on the purchase and transport of Iranian crude oil  came into force. Prior to this action, the 27 member countries of the EU used to account for 20 per cent of Iran’s oil exports.