Where stablecoin reserve data comes from

A stablecoin row on a dashboard usually carries a word — fiat-backed, crypto-backed, algorithmic — and a reader takes that word as a fact about the reserve. It is not. It is a category the dashboard assigned. The facts about a reserve are in three other places: a report the issuer prepares, an opinion an accountant signs on that report, and the law that decides which of those must exist and how often. Each one states what it covers, and the scope is where readers go wrong.

This page does not say whether any token is backed. It says which document makes which claim, as of when, and what each one leaves out.

How it works

The chain runs in one direction.

1. The issuer prepares a report. Tokens outstanding, reserve assets, their value, sometimes a composition table. It is management's document.
2. An accounting firm reports on it. Not on the token and not on the company in general: on that report, or on one assertion in it, at the dates it names, against criteria the report itself sets out.
3. Someone republishes the result. A dashboard, an aggregator, a news item. By this stage the scope and the date have usually fallen off.

The dashboard's own label is a fourth thing again. DefiLlama's stablecoins API, read on 23 October 2026, lists 425 tokens, each with a pegMechanism field: 146 are classified as fiat-backed, 27 as algorithmic and the rest as crypto-backed. The field describes the design. It carries no report, no accountant and no date, and it is not meant to.

What the two largest issuers publish

Tether: quarterly, ISAE 3000, one point in time

The most recent report on Tether's reserves is BDO Advisory Services S.r.l.'s assurance report, signed in Milan on 31 July 2026, on the Financial Figures and Reserves Report of Tether International, S.A. de C.V. as at 30 June 2026. Read what kind of document it is before reading the numbers:

• The standard. A "reasonable assurance engagement" under the International Standard on Assurance Engagements 3000 (Revised), the IAASB standard for "Assurance Engagements Other than Audits or Reviews of Historical Financial Information". It is not an audit of financial statements, and its title says so.
• The subject. The reserves report only. The report itself says it "does not represent the financial statements of the Company but discloses financial information extracted from its accounting records".
• The opinion. That the report "is, in all material respects, fairly presented in accordance with the criteria, including Management's Key Accounting Policies, set out therein".
• The figures it covers. Reserves of US$187,751,426,411; liabilities of US$183,641,897,215, of which US$183,622,105,630 relate to digital tokens issued; an excess of US$4,109,529,196 — all as of 30 June 2026 at 11:59 pm UTC.

And what it says it does not cover, in its own words: "We did not perform procedures or provide any assurance at any other date or time". The Notes to the reserves report are "for additional information only" and outside the engagement. The going-concern assessment is management's, and "we do not provide any assurance in respect of such assessment". The valuation assumes "normal trading conditions" and does not reflect "key custodians or counterparties experiencing substantial illiquidity". And the firm was engaged not by the issuer but by a third entity the report names, Tether Global Investments Fund SICAF SA.

Separately, Tether announced on 13 August 2026 that KPMG U.S. had issued an unqualified opinion on Tether International's financial statements for the year ended 31 December 2025, "in accordance with AICPA standards" in its chief executive's words. The announcement does not link the statements, and this page did not read them; it is a different document from the quarterly report, covering a period rather than a moment.

Circle: monthly, AICPA examination, one assertion at two dates

Circle's transparency page describes a "Big Four accounting firm" providing monthly assurance "prepared according to attestation standards set out by the American Institute of Certified Public Accountants", and weekly disclosure of reserve holdings. The August 2026 report is the most recent one linked there on 23 October 2026.

It is narrower than Tether's in one way and more granular in another.

• The subject is one assertion: that "the Fair Value of Assets Held in USDC Reserve is equal to or greater than USDC in Circulation" at the report dates. The accountants "examined management's assertion" and opine that the assertion "is fairly stated, in all material respects".
• Two dates, not a month. The report dates are 11 August and 31 August 2026, both at 11:59 pm UTC. Nothing between them is covered.
• The figures. USDC in circulation of 72,034,978,974 and 73,320,757,305; fair value of reserve assets of US$72,112,635,782 and US$73,398,532,613.
• The holdings, by CUSIP. Most of the reserve sits in the Circle Reserve Fund, which the report describes as "a government money market fund under Rule 2a-7 of the Investment Company Act of 1940", listed down to the individual Treasury bill and its maturity, alongside repurchase agreements and cash at regulated institutions.

"In circulation" is a defined term, and it is not on-chain supply. The report's criteria start from total supply on its approved blockchains — 74,147,014,220 on 11 August — and subtract tokens that exist but are not issued to anyone (1,982,133,877), tokens restricted under a legal order (129,865,986) and pending burns in one contract (35,383). A dashboard summing token supply across chains will show the first number; the reserve report is measured against the second. Neither is wrong; they are not the same quantity.

What the law will require, and when

United States: the GENIUS Act

Public Law 119-27, signed on 18 July 2025, sets three disclosure duties for a permitted payment stablecoin issuer:

• A monthly composition report, section 4(a)(1)(C): published on the issuer's website, containing "the total number of outstanding payment stablecoins" and "the amount and composition of the reserves", "including the average tenor and geographic location of custody of each category of reserve instruments".
• A monthly examination and certification, section 4(a)(3): "each month, have the information disclosed in the previous month-end report … examined by a registered public accounting firm", with the chief executive and chief financial officer certifying the report's accuracy to the regulator and a knowingly false certification carrying the criminal penalties of 18 U.S.C. 1350(c). The statute's text points to a month-end report "under paragraph (1)(D)"; the publication duty itself is lettered (1)(C).
• An annual audit for the largest, section 4(a)(10): an issuer with more than US$50,000,000,000 in outstanding issuance that is not already an SEC reporting company prepares GAAP financial statements, audited by a registered public accounting firm under PCAOB standards, and publishes them.

None of this is in force yet. Section 20 makes the Act effective on the earlier of 18 months after enactment or 120 days after the primary federal regulators issue final regulations. The Office of the Comptroller of the Currency issued its final rule on 21 October 2026, effective 18 January 2027, for issuers within its jurisdiction. It fixes the timing: by noon on the last day of each month, the composition report "as of noon on the last day of the previous month", in a template the rule sets out, and the accountant's examination report "published on the website of the issuer at the same time". Whether the other federal and state regulators have finalised their own rules was not checked for this page.

So the monthly and quarterly reports described above are not GENIUS Act reports. They are what the issuers publish today, under their own criteria.

European Union: MiCA

MiCA splits stablecoins into two kinds, with different reserve duties.

• Asset-referenced tokens. Article 30(1): disclose the amount in circulation and the value and composition of the reserve, "updated at least monthly". Article 36(9): "an independent audit of the reserve of assets every six months". Article 36(10): notify the result to the authority within six weeks of the valuation date and publish it within two weeks of that; Article 30(2): publish "the full and unredacted audit report". ESMA's interim register file of asset-referenced token issuers, last modified on 14 February 2025, had no entries when read on 23 October 2026.
• E-money tokens, the category for a token referencing one official currency and issued by a credit or e-money institution. Article 54 requires at least 30 percent of the funds received to be "deposited in separate accounts in credit institutions" and the rest in "secure, low-risk assets" in the same currency. The six-monthly audit of Article 36 applies under Article 58(1) only once the token is classified as significant, from the date of that decision — or under Article 58(2) where the home authority requires it. ESMA's e-money token register lists Circle Internet Financial Europe SAS, an electronic money institution supervised by the French ACPR, with white papers for EURC and USDC; whether either token has been classified as significant was not checked here.

What it costs

Reading all of this is free; every document above is public. The cost is time and lag.

• Lag. Tether's report for 30 June was signed on 31 July. Circle's August report covers 11 and 31 August and is published the following month. Under MiCA an asset-referenced token's audit can reach the public up to eight weeks after its valuation date. Under the OCC's rule the gap is one month. A dashboard showing today's supply next to the latest reserve figure is showing two different dates.
• Coverage. Every report here is about a moment, or two. None of them says anything about the days between, about how quickly reserve assets could be sold in a stressed market, or about whether redemption works for a given holder.

What you can do about it

Find the document behind the label. When a dashboard says fiat-backed, go to the issuer's transparency page and find the latest accountant's report. If there is none, the label is all there is.

Read four things on the first page of the report. The standard (an ISAE 3000 assurance report, an AICPA examination or an audit of financial statements). The subject (a reserves report, one assertion, or full financial statements). The date or dates. What is excluded — notes, going concern, other dates. Those four decide what the opinion is worth for your purpose.

Match the denominator. Before comparing a reserve figure with token supply, check how the report defines what is outstanding. Circle's in-circulation figure excludes minted-but-unissued and legally restricted tokens; on-chain supply on DefiLlama or Artemis does not. The stablecoin entry covers which tokens those vendors count in the first place.

Date every number you put next to another. A reserve figure from the end of last month and a supply figure from this morning are not a ratio. Write the as-of date of each next to it.

Check the register, not the press release. In the EU, ESMA's interim registers say who is an authorised e-money or asset-referenced token issuer. In the US, from the Act's effective date, the monthly report and the accountant's examination report are both required on the issuer's own website; their absence after that date is itself information.

Do not stop at "attested". An attestation answers the question its scope states, at the dates it states. If your question is about liquidity under stress or about redemption terms, the documents to read are the issuer's redemption policy and, from 2027, the US regulators' rules — not the reserve report.