Stablecoin issuer reserves — the assets that back the dollar-pegged tokens used onchain — are one of the most-discussed and least-understood parts of stablecoin operations. The headline claim ("backed 1:1 by U.S. dollars") is almost always more nuanced than the slogan. Some reserves are cash at banks; some are short-duration U.S. Treasuries in money market funds; some are commercial paper, secured loans, or onchain collateral. Custody varies — bank deposits, trust accounts, broker-dealer accounts, smart contracts. Attestation cadence ranges from quarterly point-in-time reports to real-time onchain visibility. This article walks through where the reserves of the five largest stablecoin issuers actually sit, the difference between an audit and an attestation, and how to read the transparency reports without taking the slogan at face value.
The reserve question matters because stablecoin holders are unsecured creditors of the issuer (or, for crypto-collateralized tokens, dependents on smart-contract integrity). The answer to "what backs this token" is the answer to "what happens if I try to redeem at par when something goes wrong." Combined stablecoin supply crossed $235B in early 2026, and the reserve composition is the load-bearing detail behind every dollar of that supply.
What Are Stablecoin Reserves?
Stablecoin reserves are the assets an issuer holds against outstanding token supply. For fiat-backed tokens, reserves are typically cash, short-duration U.S. Treasuries, money market fund shares, and (in some cases) commercial paper, secured loans, or other instruments. For crypto-collateralized tokens, reserves are the onchain collateral locked in vaults plus, in Sky's case, the USDC held in the Peg Stability Module. For synthetic dollars like USDe, "reserves" is a stretched term — what backs each token is the combined long-spot + short-perp position, not a static asset pool.
The U.S. Treasury's 2025 TBAC presentation on stablecoin demand drivers separates these models explicitly because they affect Treasury market plumbing differently. Fiat-backed issuers buy bills directly — Tether and Circle combined are among the largest non-government holders of short-duration Treasuries globally. Crypto-collateralized issuers do not.
Where the Reserves Actually Sit
Below is the reserve structure for each of the five major issuers, sourced to public disclosure as of early 2026.
Circle (USDC)
~80%+ in the Circle Reserve Fund (USDXX): A registered 2a-7 government money market fund managed by BlackRock and held at BNY Mellon. The fund holds short-duration U.S. Treasuries (under 60 days weighted-average maturity) plus overnight repurchase agreements collateralized by Treasuries.
Remainder as cash deposits at GSIB banks: BNY Mellon, Customers Bank, Cross River Bank, and others. CUSIP-level Treasury holdings are published daily on the BlackRock fund page; Circle's transparency page aggregates this data.
Post-SVB (March 2023), Circle consolidated banking relationships toward the Reserve Fund structure. The reserve mix today is materially different from the 2022 mix; USD-backed stablecoin infrastructure covers the broader rail.
Tether (USDT)
~80% in U.S. Treasuries: Direct holdings, repo positions, and money market fund shares. Tether is among the largest non-government holders of short-duration U.S. Treasuries globally.
~5% in gold: Held physically in vaults and indirectly via XAUT.
~3% in Bitcoin: Excess reserve buffer.
~5% in secured loans: Down materially from the 2022 mix; Tether has reduced secured-loan share over multiple quarters.
Remainder in cash, money market instruments, and other investments.
Tether reports excess reserves of $5–10B above outstanding USDT supply, sitting in the more volatile categories (BTC, gold) as a loss-absorbing buffer. The full breakdown is published quarterly on tether.to/en/transparency.
Paxos (USDP, PYUSD)
1:1 in cash at FDIC-insured banks and short-duration U.S. Treasuries. Per-token segregation under the NYDFS Trust Charter — PYUSD reserves are held in a separate trust account from USDP reserves.
Trust Charter structure: Reserves are held by Paxos Trust Company in fiduciary capacity, off the corporate balance sheet. In a Paxos insolvency scenario, the reserves would be available to token holders ahead of Paxos creditors.
Paxos publishes monthly Withum attestations specific to each token issued; paxos.com/transparency hosts the reports.
Sky (DAI, USDS)
Crypto vaults: ETH, staked ETH (stETH, wstETH), wBTC locked in onchain Vaults, observable on Etherscan.
USDC Peg Stability Module: A 1:1 USDC↔DAI swap pool that lets USDC effectively back DAI. The PSM is a major share of DAI's effective backing.
RWA (Real-World Asset) Vaults: Tokenized U.S. Treasuries via Monetalis, BlockTower, and others. RWA holdings cross $1.5B+ in early 2026 and are the largest single source of protocol revenue.
D3M (Direct Deposit Module): DAI directly deposited into Aave, Compound, and Spark to balance lending markets.
All onchain components are observable in real time on MakerBurn and DeFiLlama; off-chain RWA legs require trust in the partner attestations. The MakerDAO/DAI primer covers the full breakdown.
Ethena (USDe)
Long staked-asset collateral: wstETH, rsETH, ETHx, mSOL, jitoSOL, wBTC. Held in custody via off-exchange settlement providers (Copper, Ceffu, Cobo, Fireblocks) outside the perpetual venue while the position is open.
Short perpetual hedge: Equivalent notional short positions on Binance, Bybit, OKX, Deribit. The combined long-spot + short-perp is the "synthetic dollar."
USDtb: A portion of reserves now sits in USDtb, Ethena's institutional Treasury-backed product, providing a fiat-stable buffer outside the delta-neutral structure.
Reserve Fund: ~$80M+ buffer above per-token collateral, funded from protocol revenue. Absorbs adverse funding-rate periods and tail risk.
Real-time per-venue collateral is published on app.ethena.fi/dashboards/transparency.
Audit vs Attestation
"Audit" and "attestation" describe different review structures and the distinction matters when reading reserve disclosures.
Audit: A full opinion under GAAS (AICPA) or PCAOB standards, covering financial statements over a reporting period. Annual cadence. Provides a substantive opinion ("the financial statements present fairly...").
Attestation: An agreed-upon-procedures report under AICPA AT-C 105 or 215 standards. Reviews a specific assertion at a specific point in time (e.g., "at 5:00pm on March 31, reserves matched outstanding supply per the disclosed categories"). Monthly or quarterly cadence. Does not provide a substantive opinion on the entity's financial statements.
Most stablecoin reserve disclosures are attestations because monthly audits are operationally infeasible and because the reserve assertion is the customer-relevant question. Circle (Deloitte, monthly), Paxos (Withum, monthly), and Tether (BDO, quarterly) all publish attestations. Circle's parent entity is also subject to PCAOB-standard audits as part of S-1 / IPO disclosure requirements — that's a layered structure of monthly token attestation plus annual entity audit.
Sky has no off-chain reserves to attest to. The collateral is observable in real time onchain. The trust shift is from "trust the attestation" to "trust the smart contracts and the data feeds" — a different risk model, not categorically lower.
How to Read Transparency Reports
A practical reader's checklist:
Cadence: Monthly is more current than quarterly. Real-time onchain data is more current than either, with the trust-shift caveat above.
Granularity: CUSIP-level Treasury holdings (Circle does this) are more verifiable than aggregated category breakdowns.
Scope: The attestation should cover the specific token's reserves and explicitly state that supply matches reserves on the reporting date. Vague language ("our reserves are sufficient") is weaker than specific assertions.
Custodian disclosure: Which banks, broker-dealers, or smart contracts hold the assets. Concentration in a single counterparty is a risk factor.
Auditor identity: Big Four firms apply more stringent procedures than smaller firms. Tether's BDO Italy is reputable; Withum (Paxos) is mid-tier; Deloitte (Circle) is Big Four.
Excess reserves: Reserves above 1:1 backing function as loss-absorbing buffers. Issuers that disclose excess reserves separately are more transparent than those that don't.
What Reserves Don't Cover
Reserve disclosures address solvency at a point in time. They don't address:
Operational risk: Hacks, key compromise, smart contract bugs.
Counterparty risk: Bank failure (the 2023 SVB event), broker-dealer insolvency, perpetual venue insolvency.
Liquidity risk: A 1:1 reserve in 90-day Treasuries cannot be liquidated instantly at par for a same-day mass-redemption event without secondary-market spread.
Regulatory risk: An issuer's authority to operate can be withdrawn (Paxos / BUSD precedent).
Bridge risk for cross-chain supply: Tokens bridged to non-canonical chains via wrapped representations carry the bridge's risk separate from the issuer's reserves.
The combination of all these factors is what determines real-world stablecoin risk. Reserve composition is the load-bearing detail but not the entire story. Compliance tools covers the operational layer.
Eco's Role
Eco operates above the issuer layer, routing tokens issued by Circle, Tether, Paxos, Sky, and Ethena across 15+ supported chains. The orchestration layer is issuer-agnostic — teams choose the issuer that fits their compliance and use case (USDC for regulated payments, PYUSD for PayPal flows, USDT for emerging-market settlement, DAI/USDS for DeFi, USDe for yield), and Eco handles the cross-chain plumbing without taking a position on which reserve model is "correct" for a given use case.
FAQ
What's the difference between an audit and an attestation?
An audit is a substantive opinion on financial statements under GAAS or PCAOB standards, typically annual. An attestation is an agreed-upon-procedures report on a specific assertion (e.g., reserves match supply) at a point in time, typically monthly or quarterly. Stablecoin reserve disclosures are mostly attestations because monthly audits are operationally infeasible.
Where does USDC reserve actually sit?
~80%+ in the BlackRock-managed Circle Reserve Fund (USDXX), held at BNY Mellon. The fund holds short-duration U.S. Treasuries plus overnight Treasury-collateralized repo. The remaining cash deposits sit at G-SIB banks. CUSIP-level holdings are published daily.
Why does Tether hold Bitcoin in reserves?
Tether holds ~3% of reserves in Bitcoin as part of the excess reserve buffer — the assets above the 1:1 USDT backing. The BTC and gold positions function as a loss-absorbing layer that does not count toward the per-token reserve assertion.
Are crypto-collateralized stablecoins audited?
Sky (DAI/USDS) does not have off-chain reserves to attest to — the collateral is observable in real time onchain via Etherscan, MakerBurn, and DeFiLlama. The exception is the RWA exposures, which require trust in the partner's off-chain attestations (Monetalis, BlockTower).
What happens if a stablecoin issuer's bank fails?
Reserves held at a failed bank are subject to FDIC limits ($250K per account holder per bank) for cash deposits — irrelevant for amounts in the billions. Cash held in a money market fund or in custody at a broker-dealer (BNY Mellon for the Circle Reserve Fund) is segregated from the bank's general assets and survives bank failure. The 2023 SVB event illustrated this distinction; stablecoin swap aggregators covers the broader operating context.