Stablecoin issuer Tether said it helped authorities freeze nearly $550 million in Iran-linked USDT during 2026, as a Senate Democrat called for an investigation into the stablecoin issuer on Monday.

In a statement on Monday, the company said it has been working closely with international law enforcement for years. This year alone, it froze more than $130 million in USDT across four wallets, and in April, it froze more than $344 million linked to the Central Bank of Iran. 

“Tether has consistently demonstrated that USDT is not a haven for sanctioned actors, terrorist organizations or criminal networks,” said Tether CEO Paolo Ardoino.  

The statement from Tether came as Democratic investigators on the Senate Permanent Subcommittee on Investigations released a report alleging USDT had become a key channel for Iran to evade sanctions. 

Investigators found that 84% of 846 crypto wallets sanctioned over ties to Iran had transacted exclusively or nearly exclusively in USDT. The findings prompted US Senator Richard Blumenthal to call on the Treasury and Justice departments to investigate potential sanctions violations.

Tether said its cooperation with authorities globally had resulted in more than $4.9 billion in assets being frozen, including more than $2.4 billion connected to US authorities. 

“The record is public: the DOJ, FBI, Secret Service, HSI, OFAC and authorities around the world have repeatedly worked with Tether to trace, freeze and recover assets. We will continue to make that capability available to authorities working to stop terrorism, sanctions evasion, fraud and other serious crimes,” Ardoino said. 

Related: Manhattan US Attorney leading probe into Binance’s Iran compliance: Bloomberg