Iran’s battered currency took another significant dive on Sunday against major currencies, breaching the 150,000 rial to the dollar threshold. The currency was trading at around 138,000 to the dollar in the past two weeks.

The rial gained back some ground later in the day, but usually devaluations in Iran happen first with thresholds being broken and then more long-lasting lows taking hold.

Iran’s currency has lost value almost fourfold in the past 15 months, as the U.S. withdrew from the 2015 nuclear agreement and began reimposing sanctions on the Islamic Republic. Besides the sanctions, Iran’s economy also suffers from serious structural issues and corruption.

The government still offers cheaper dollars to businesses importing essential and strategic goods, but members of parliament and others criticize the policy for potential corruption, as profiteers find ways to get the cheaper dollars by fraudulent documents.

One member of parliament told Mehr news agency Sunday that brokers and middlemen have taken advantage of the government and made around $14.2 billion in profits in 2018-2019.

Meanwhile Iran’s parliament passed a resolution on Sunday to begin an investigation of Iran Central Bank’s five-year record in handling currency issues and its regulatory duties. The banking system is in a precarious situation as multiple corruption cases, costing the government billions of dollars have been reported.

Political influence by regime insiders in Iran make it very hard to regulate and supervise government-supported economic enterprises and banks.