Tether has hired a Big Four accounting firm for a full audit for the first time in its history. This review covers all USDT reserves totaling $184 billion. As a result, the world's largest stablecoin issuer is now moving beyond its previous quarterly attestations.
Tether did not disclose the name of the firm. According to the company, the onboarding phase concluded several weeks ago. During that time, the auditor analyzed Tether's internal control systems and financial reporting. In scope are digital assets, traditional reserves, and tokenized liabilities. Still, Tether did not provide a specific completion date.
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Attestation vs. audit: a key distinction
Until now, Tether published quarterly attestation reports through BDO Italia. These attestations provide a snapshot of reserves at a specific reporting date. However, internal control systems remain unexamined. A full audit goes significantly further, examining assets, liabilities, internal controls, and reporting systems over an extended period.
This gap is precisely where critics have focused for years. S&P Global rated USDT as "weak" in 2025, warning of potential undercollateralization amid further Bitcoin price declines. In 2021, the CFTC settled with Tether for $41 million over misleading statements about its reserves. Since then, the company has gradually increased transparency but never delivered a full audit. CFO Simon McWilliams emphasized the selection process:
"The Big Four firm was selected through a competitive process because the organization already operates at Big Four audit standards." - Simon McWilliams, CFO, Tether
Tether Big Four audit in the regulatory context
The timing of the announcement coincides with a period of tightening regulatory requirements. Specifically, President Trump signed the GENIUS Act into law in July 2025, the first US federal legislation on digital assets. It requires stablecoin issuers with more than $50 billion in volume to undergo annual audits.
However, the GENIUS Act primarily applies to US-regulated issuers. Tether is domiciled in El Salvador and does not fall directly under the law. Senator Jack Reed therefore introduced bill S.3907, which would also require foreign stablecoin issuers to submit to audits. Consequently, Tether's decision to pursue a voluntary Big Four audit preempts this potential regulation.
At the same time, personnel ties exist between Tether and US politics. Commerce Secretary Howard Lutnick, formerly CEO of Cantor Fitzgerald, stated at a Senate hearing: "Tether should be audited." Cantor Fitzgerald manages portions of Tether's reserves and holds roughly 5 percent of the company.
Reserves of $193 billion and $10 billion in profit
According to the most recent attestation report for Q4 2025 by BDO Italia, Tether's total reserves stand at $193 billion. Liabilities amount to $186.5 billion, with surplus reserves of $6.3 billion. Overall, USDT accounts for roughly 60 percent of the total stablecoin market, which exceeds $300 billion.
Reserve composition underscores Tether's weight in the traditional financial system. Specifically, the company holds $141 billion in US Treasury securities, of which $122.3 billion are in T-Bills. This makes Tether one of the largest non-sovereign holders of US government debt worldwide. In addition, gold reserves add another $17.4 billion, and Bitcoin holdings total $8.4 billion. Annual net profit for 2025 exceeded $10 billion. Meanwhile, the user base grew to over 550 million people globally.
CFO McWilliams as architect of the transparency strategy
Tether appointed Simon McWilliams as CFO in March 2025 with the explicit mandate to advance the full audit. McWilliams brings over 20 years of experience in financial leadership roles. Previously, he served as CFO at LetterOne, a treasury unit with $15 billion in assets. He also held the role of COO at Quantmetrics Capital Management. His qualifications include CPA, CGMA, and degrees from IE Business School and INSEAD.
His predecessor Giancarlo Devasini, founder and principal shareholder of Tether, led the finance department for ten years. He subsequently moved to the position of group chairman with a focus on macro strategy. Already a year before the announcement, the leadership change signaled the strategic shift toward institutional audit standards.
A distinction is worth noting here. In February 2026, Deloitte confirmed the attestation for USAT, a US-regulated stablecoin issued by Anchorage Digital with Tether participation. By contrast, the Big Four audit announced today concerns USDT itself and represents a separate process.
