Stablecoins Enter the Money-Market Stack

The GENIUS Act, signed on 18 July 2025 as Public Law 119-27, directs payment-stablecoin reserves into a specific set of assets, and Treasury bills are the largest of them. That market has grown from 1.43 trillion dollars outstanding in 2015 to 6.99 trillion in July 2026, and from 11.2 per cent of marketable Treasury debt to 22.2 per cent. Whatever demand a regulated stablecoin sector generates arrives into a market that has roughly quintupled while nobody was discussing stablecoins at all.

Figure 1 shows that market and then does something deliberately modest with it. The panel below is a scenario, not an estimate: it supplies a measured denominator and leaves the redemption size as the reader's own input, because no independent daily source measures aggregate issuer float and monthly attestations are neither standardised nor independent statistics.

Section 01What the Act actually built

A payment stablecoin joins two balance sheets. On one side is a transferable token designed to hold a fixed monetary value. On the other is an issuer holding permitted reserves and operating a conversion process. The statute's requirements read like a money-market prospectus: reserve backing on at least a one-to-one basis in a defined list of permitted assets, segregation of those reserves, published redemption policy, and monthly public disclosure of reserve composition.

The family resemblance to money-market instruments is close, and the categories should still not be collapsed. A regulated payment stablecoin resembles a money-market fund, a bank deposit and central bank money without being any of the three: it remains a par-denominated liability of a private issuer, redeemable through a process the issuer defines, backed by assets the issuer holds. Each of those clauses carries a different risk, and only the last one is about credit.

Section 02Into the money-market stack

Two linkages follow, and they behave differently. The first is reserve demand: to the extent issuers hold Treasury bills, Treasury-backed repo, or government money-market funds, the sector becomes a buyer in short-dated dollar markets, and its aggregate size determines whether that matters. The scenario panel of Figure 1 bounds the arithmetic. A 50 billion dollar redemption represents 0.72 per cent of bills outstanding; 200 billion represents 2.86 per cent. Against the stock of the bill market, plausible redemption volumes are small.

That is a genuine result and a limited one. It compares a flow against a stock, which is the wrong comparison for a stress. What matters in a stress is the flow against the market's capacity to absorb it on the day, and this research does not have daily bill transaction volumes to make that comparison. The honest statement is that the stock arithmetic gives no cause for alarm and does not settle the question.

The second linkage is temporal, and no amount of reserve quality fixes it. Tokens transfer continuously. Primary redemption depends on issuer eligibility rules, banking rails, cut-off times, and reserve markets with limited operating hours. A holder who wants dollars at three in the morning on a Sunday is transacting in a secondary market, at whatever price that market offers, against reserves that cannot be liquidated until Monday. The reserves may be immaculate and the mismatch still exists.

token_value  =  par, by design, enforced by an arbitrage:

    if token trades below par, an eligible holder redeems at par
    and profits.  That requires:

        (a) eligibility to redeem at all
        (b) an open redemption window
        (c) the issuer able to fund conversions from reserves
        (d) reserves saleable at par, on the day

measured context, July 2026:
    Treasury bills outstanding        $6.99 tn
    marketable Treasury debt         $31.46 tn      bills = 22.2%
    3-month bill yield                 3.92%        (0.83% mean, 2015-2021)

Section 03Where liquidity risk remains

Par is maintained by a mechanism, not by nomenclature. Eligible holders must be able and willing to exchange discounted tokens for dollars, and the issuer must fund those conversions without delay. Both conditions can hold in normal weather and fail together in bad weather, which is the general property of arbitrage-enforced pegs and not a criticism specific to this statute.

The yield on those reserves is worth a sentence, because it changes the incentives. It is not plotted in Figure 1, which has room for the size of the market and the scenario but not for a third series. Three-month bills yielded an average of 0.83 per cent between 2015 and 2021 and 4.68 per cent between 2023 and 2026. A reserve portfolio that earns nothing and a reserve portfolio that earns nearly five per cent are different businesses, with different pressure on the issuer to reach for yield inside the permitted set and different consequences if rates fall back.

Read as plumbing, a stablecoin is a redeemable par liability on a rail that stays open after its reserve markets close.

None of this is an argument against the Act. Segregation, par redemption and monthly disclosure materially strengthen the arrangement relative to an unregulated reserve claim. The useful classification is by layer rather than by sector: token layer, liability structure, reserve layer. The Act constrains the third tightly, the second moderately, and the first not at all, and the first is where the continuous-settlement mismatch lives.

This research is analysis and commentary for general information. It is not investment advice, an offer, or a solicitation, and it contains no price forecasts. Quantities in the text are the author's own calculations from the Treasury sources cited; descriptions of the law summarise the statute.