of Iran’s ports and imposes more sanctions on its oil exports, Tehran is confronting another problem: billions of dollars in revenue from previous oil sales that it says have gone missing.

A spokesperson for Iran’s judiciary said in September that a network of oil intermediaries known as “trustees” owed the Iranian government between 10 billion euros ($11bn) and 11 billion euros ($12bn). That figure was equivalent to half of the total oil revenue projected in Iran’s government budget for the current fiscal year.

US officials, including Treasury Secretary Scott Bessent, have tied Iran’s struggles to access oil revenues as evidence that its economic pressure campaign is having an effect. In August, Bessent said that “Iran’s shadow banking system was buckling” under pressure from the US campaign against the country, which has been ramped up as Washington seeks a way to force Tehran to capitulate in the war between the two countries, launched by the US and Israel in late February.

So who are the oil intermediaries, why does Iran depend on them, and what has happened to the billions of dollars they owe? Let’s take a closer look. Who are Iran’s oil intermediaries?

The debt, and the crisis it has created for the Iranian government, both stem from an oil-sales arrangement Tehran adopted in 2012 in response to US sanctions targeting Iranian oil exports.

American and European sanctions targeting Iranian oil sales and revenue collection began in 2012. The stated rationale behind both sets of measures was that revenue from oil sales helped finance Iran’s nuclear programme and that restricting Iranian oil exports could prevent the programme from advancing.

In response, the Iranian government devised a way to circumvent international sanctions on its oil sales. Unable to sell oil through the Oil Ministry and receive the proceeds through the Central Bank, it began selling oil to domestic buyers or using it to settle outstanding obligations to institutions and organisations owed money by the state.

This arrangement gave rise to a network of oil intermediaries often referred to in Iran as the “trustee network”. Rather than selling all its oil through official government channels, the state entrusted crude oil to institutions, individuals and companies to sell on its behalf. The proceeds were supposed to be transferred to the government’s treasury, with the sellers or recipient institutions subsequently recovering their agreed costs and outstanding claims. Some institutions sold the oil themselves, while others contracted private trading companies to handle the sales.

The Oil Industry Pension Fund, established for retired Oil Ministry employees familiar with the oil-sales process, was among the first institutions to receive crude oil for sale. Other recipients included Khatam al-Anbiya Construction Base, a major hub for large-scale infrastructure projects. Even the municipal police received payments owed to them by the government in the form of crude oil.

Effect of the nuclear deal Even in those early experiments, discrepancies emerged between the revenue expected from oil sales and the amounts sellers actually deposited into the government’s treasury. These discrepancies eventually gave rise to some of Iran’s largest economic corruption cases.

The accounting discrepancies and the government’s inability to recover money from private sellers entrusted with Iranian oil persisted until 2016, when the Joint Comprehensive Plan of Action (JCPOA) nuclear deal was signed and when sanctions on Iranian oil sales were lifted. The government was subsequently able to regain control over oil sales.

Individuals who had sold Iranian oil but failed to return the proceeds were imprisoned. With the ability to sell oil again through legal and transparent channels, the government was able, for a time, to manage its oil revenues and spending with greater control. How did money from oil sales go unreturned?

After US President Donald Trump withdrew the United States from the JCPOA in 2018 during his first presidential term, the Iranian government once again had to rely on private oil traders to sell its oil. But the problems associated with selling oil through intermediaries rather than official state channels, including delays in returning revenues, accounting discrepancies, debts owed by oil sellers to the government, and the occasional seizure of Iranian oil shipments at sea, once again constrained the government’s ability to manage its oil revenues.

Moreover, the US expanded its sanctions beyond Iranian government institutions and interests, adding bank accounts involved in transactions with the Iranian government, currency-exchange offices, companies, and individuals to its sanctions lists. As a result, the time between individuals participating in Iran’s oil-trading network and being sanctioned themselves, along with their assets and companies, and having their accounts blocked or frozen grew progressively shorter.

This contributed to an accumulation of debts owed by sanctioned oil traders – no longer able to access their accounts – to the government. It also left Iran with little choice but to expand its private oil-sales network. That meant increasing the number of people involved in trading Iranian oil, reducing the volume of oil allocated to each individual or company and, ultimately, increasing the risk that the proceeds would not be returned.

Iranian officials have also accused trustees of exploiting the sanctions workarounds to enrich themselves The billions of dollars owed by private oil sellers to the Iranian government are a combination of outstanding payments, disputed financial obligations and allegations of corruption. Iran’s judiciary chief recently addressed the issue, warning that oil sellers who refuse to return the proceeds from oil sales will face legal action. But such warnings do not change the sanctions environment or remove the obstacles that prevent some oil sellers from returning the money.