Stablecoins as payment rails

1. TL;DR

Stablecoins are increasingly used as payment infrastructure rather than only as DeFi trading collateral: Solana’s sub-cent, sub-second transfers make the “convert local currency → stablecoin → convert back” pattern viable for cross-border payments, purpose-built protocols like Solana Pay standardize point-of-sale QR-code payments, and Stripe and Paradigm’s Tempo is a payments-first blockchain designed to let businesses settle in stablecoins the way they settle card payments today. The GENIUS Act, signed 2025-07-18, gives the U.S. its first comprehensive federal framework for “payment stablecoins,” but the rulemaking that will determine the actual rules — including whether issuers can share reserve yield with users as rewards — was still in progress as of 2026-08, and Paradigm has argued that a proposed restriction on those rewards misunderstands how stablecoin economics work (see /stablecoins/pegs-and-psm/).

2. Explain it simply

Analogy

Sending money internationally today often works like mailing a package through five different courier companies, each one repacking it, charging its own fee, and taking a day to hand it to the next courier — that’s what a chain of correspondent banks does to a wire transfer. A stablecoin payment rail is closer to handing the package directly to a courier who can deliver it anywhere in the world in under a second, then having someone local unpack it into the currency the recipient actually wants.

ELI5

Instead of your money passing through several different banks to reach someone in another country — each one taking a cut and a day or two — a stablecoin payment lets it move directly, in under a second, for a tiny fraction of a cent. A phone or point-of-sale device shows a code; scanning it fills in who gets paid, how much, and a note to match the payment up later. Someone on the other end then swaps the digital dollars for the local currency and deposits it in a normal bank account, so neither the payer nor the recipient necessarily has to think about the blockchain underneath at all.

Step-by-step walkthrough

Scenario: Ana runs a shop and wants to accept a payment from Ben, a customer paying with USDC via Solana Pay.

Before. Ben’s wallet holds 50 USDC. Ana’s point-of-sale app has generated a Solana Pay QR code encoding a Transfer Request: Ana’s wallet address, an amount of 50 USDC, and a unique reference ID for reconciliation.
Scan. Ben scans the QR code with his phone’s wallet app, which parses the URL and shows him “Pay Ana’s Shop 50 USDC” without requiring him to manually type an address.
Sign and submit. Ben approves; his wallet builds and signs the transaction and submits it to Solana. The network confirms it in well under a second for a fraction of a cent in fees.
Reconciliation and off-ramp. Ana’s payment processor watches for the reference ID, matches the incoming 50 USDC to Ben’s order, and converts it to Ana’s local currency through an off-ramp partner, depositing the equivalent into her bank account — typically within minutes.
After. Ben’s wallet shows 50 USDC less; Ana’s bank account shows the local-currency equivalent. No card network, correspondent bank, or multi-day settlement window was involved in the payment leg itself.

Common misconceptions

Myth: using stablecoins for payments requires both sides to understand crypto. Reality: Solana Pay’s own documentation frames it as “a standard protocol & set of reference implementations that enable decentralised payments” behind a QR code — merchants and customers can interact with amounts in local currency and a scan, never seeing a wallet address.
Myth: Tempo is just another Ethereum layer-2 rollup. Reality: Tempo is an independent, EVM-compatible layer-1 blockchain (not a rollup) built on the Reth execution client with its own consensus, incubated jointly by Stripe and Paradigm with design input from Visa, Shopify, DoorDash and several banks (multiple contemporaneous reports, 2025-09 and after).
Myth: the GENIUS Act legalizes any stablecoin issuer. Reality: it specifically defines and regulates “payment stablecoins,” requiring issuers to be federally or state-chartered under specific reserve, redemption and audit rules — unauthorized issuance is a federal enforcement matter, not a gray area.
Myth: stablecoin holder rewards work like credit-card cashback, funded by a merchant fee. Reality: per Paradigm’s critique of a proposed rewards restriction, stablecoin rewards are funded by continuous yield on reserve assets (like Treasuries), not by a per-transaction merchant fee — see /stablecoins/pegs-and-psm/ for the full argument.
Myth: the “stablecoin sandwich” (local fiat → stablecoin → local fiat) is a niche DeFi trick. Reality: Helius frames it as one of the most impactful and already-common uses of stablecoins, powering real remittance and B2B payment flows today (see /stablecoins/fiat-backed-and-cctp/).

If you only remember one thing

A stablecoin payment collapses a multi-day, multi-intermediary correspondent-banking chain into one near-instant blockchain settlement leg bracketed by two fiat conversions — the hard engineering problem has moved from moving the money to building trustworthy, compliant ramps on either end.

3. How it works

The rail comparison

A traditional cross-border payment typically routes through a chain of correspondent banks connected by SWIFT messaging, each hop adding a fee and settlement delay; Helius describes the resulting cost and speed gap plainly: retail cross-border payments “can consume up to 6% of the transaction value,” with remittances averaging “around 6.6% globally for sending a modest sum like $200,” and settlement often taking “2-5 days or longer” (Helius, “Stablecoin Payments Guide,” as of 2025). A stablecoin rail replaces the chain of correspondent banks with a single blockchain settlement leg — Helius reports Solana peer-to-peer transfers costing “less than $0.01” and settling “in under one second” (Helius, “Solana’s Stablecoin Landscape,” as of 2025-05) — bracketed by an on-ramp (local fiat → stablecoin) and off-ramp (stablecoin → local fiat) on either end.

Solana Pay’s protocol design

Solana Pay defines itself as “a standard protocol & set of reference implementations that enable decentralised payments,” built around two URL formats (Helius/Solana Pay documentation, fetched 2026-08-29). A Transfer Request is “a non-interactive request for a transfer of SOL or SPL Tokens,” encoding a recipient address, an amount, an optional SPL token mint, and a reference field used for reconciliation and idempotent payment detection — the field Ana’s processor watches in §2’s walkthrough. A Transaction Request is more general: “almost any Solana transaction can be converted into a valid Solana Pay URL,” letting a merchant request an arbitrary smart-contract interaction rather than a plain transfer. Both formats can be encoded as QR codes, which the documentation notes “removes the barrier of needing to connect your wallet to interact” — a customer scans and approves rather than manually connecting a wallet to a website.

Tempo: a payments-first chain

Tempo is described by Paradigm as “a payments-first blockchain incubated by Stripe and Paradigm,” built because “much of today’s crypto stack either explicitly or implicitly caters to trading… but is comparatively underoptimized for payments” (Paradigm, “Tempo: The Blockchain Designed for Payments,” 2025-09-04). Design input came from “global leaders in AI, e-commerce, and financial services: Anthropic, Coupang, Deutsche Bank, DoorDash, Lead Bank, Mercury, Nubank, OpenAI, Revolut, Shopify, Standard Chartered, Visa, and more.” Technically, Tempo is an EVM-compatible layer-1 running the Reth execution client with Simplex Consensus (via Commonware), targeting sub-second finality and very high throughput; transaction fees are paid in stablecoins through a built-in fee-conversion mechanism rather than a volatile native gas token, and the network launched mainnet in March 2026 with validators initially bootstrapped from its design partners ahead of a stated transition to permissionless validation (multiple contemporaneous industry reports, 2025-09 through 2026; not from Paradigm’s own writing directly).

The GENIUS Act framework

The GENIUS Act (Guiding and Establishing National Innovation for U.S. Stablecoins Act), signed 2025-07-18, “erects a clear, first-of-its-kind framework for stablecoins,” letting “issuers… choose between federal or state supervision and get straightforward guardrails on reserves, redemption, audits, and more” (Paradigm, “The GENIUS Act Passed – Now the Real Work Begins,” 2025-07-29). Issuers with under $10 billion in circulating tokens may opt for state oversight if the state’s regime is certified “substantially similar” by a Treasury-chaired Stablecoin Certification Review Committee; above $10 billion, issuers must transition to federal oversight absent a waiver. Foreign-registered issuers may be authorized if their home regime is deemed “comparable” to U.S. standards — a determination whose implementing rules were not yet finalized as of 2026-04 (see /stablecoins/fiat-backed-and-cctp/). The Act requires 21 separate rulemakings across Treasury, the OCC, the NCUA, the FDIC and the Federal Reserve, with a one-year deadline for most required rules (2026-07-18) and full implementation 18 months after enactment (2027-01-18) (Paradigm, “An Interactive Guide to GENIUS Implementation,” 2026-04-08).

4. Worked numeric example

Compare Ana’s 50 USDC payment from §2 against a hypothetical traditional cross-border card/wire alternative for the same amount:

Leg	Stablecoin rail (Solana)	Traditional cross-border rail
Network/settlement fee	~$0.00025 per transaction (Helius, “Stablecoin Payments Guide,” as of 2025)	Bundled into card/wire fees below
Total transfer cost (fee as % of $50)	Blockchain leg: $0.00025 / $50 = 0.0005%; add an illustrative 1% off-ramp conversion fee ($0.50) for a total of about $0.50025, or roughly 1.0% of the transfer	Retail cross-border fees “can consume up to 6%” of transaction value; remittances average “around 6.6% globally” for a $200 transfer (Helius, as of 2025) — applying the low end of that range to $50 gives roughly $3.00
Settlement time	Under 1 second for the blockchain leg; minutes for off-ramp processing	“2-5 days or longer” for the traditional cross-border leg (Helius, as of 2025)

On this illustrative comparison, the stablecoin rail’s total cost (blockchain fee plus a representative off-ramp fee) comes in at roughly one-sixth of the low end of Helius’s cited traditional cross-border fee range, while settling in minutes rather than days. The blockchain-fee figure ($0.00025) and the traditional-rail percentage ranges are both sourced; the 1% off-ramp fee is an illustrative assumption for a representative on/off-ramp provider, not a specific sourced figure, since off-ramp pricing varies by provider and corridor.

5. Where it’s used

Ethereum

Tempo — an independent EVM-compatible layer-1 (not an Ethereum rollup) incubated by Stripe and Paradigm, purpose-built for stablecoin settlement, payroll, remittances, and “agentic payments”; mainnet launched March 2026 (Paradigm, 2025-09-04; corroborating industry reporting, 2025–2026). tempo.xyz
Circle Payments Network (CPN) — a payment-network product connecting regulated financial institutions for stablecoin-based settlement, referenced alongside permissioned payment infrastructure in Helius’s stablecoin payments guide.
Ethereum mainnet and its L2s — still the base settlement layer for the largest share of USDC/USDT payment volume by value, though with higher gas costs and slower confirmation than purpose-built payment chains (see /foundations/fee-markets/).

Solana

Solana Pay — the QR-code/URL payment standard this page’s walkthrough is built around; adopted by point-of-sale integrations and e-commerce platforms. [Solana Pay documentation, via Helius, fetched 2026-08-29]
Stablecoin sandwich flows — Solana’s low fees and 400ms finality make it a preferred settlement layer for the local-fiat → USDC → local-fiat pattern described in /stablecoins/fiat-backed-and-cctp/; Sphere’s SpherePay/SphereNet products connect this to real-time payment systems like Brazil’s Pix, India’s UPI and the U.S. FedNow (Helius, as of 2025-05).
Spherenet — a permissioned blockchain built on a modified Solana Virtual Machine by Sphere and Anza, designed as “a shared, compliant ledger for regulated financial entities worldwide” for cross-border settlement (Helius, “Stablecoin Payments Guide,” as of 2025).
Stablecoin debit cards (KAST, Fuse, Solayer’s Emerald Card, and others) — link on-chain Solana stablecoin balances to everyday card spending; see /stablecoins/fiat-backed-and-cctp/ for details.

6. Risks, attacks, and incidents

Rulemaking uncertainty during the GENIUS transition window. With 21 required rulemakings and a nominal 2026-07-18 deadline, Paradigm itself cautions the deadline “is an official one, but probably not the real one,” pointing to the Dodd-Frank Act’s over 400 mandated rulemakings, of which “dozens remained incomplete” more than a decade later, as historical precedent for slippage (Paradigm, “An Interactive Guide to GENIUS Implementation,” 2026-04-08). Builders designing payment products around a specific rules timeline carry real execution risk if rules slip.
Foreign-issuer and rewards-rule ambiguity. The “comparable” standard for foreign issuers and the outcome of the rewards-restriction fight (see /stablecoins/pegs-and-psm/) were both unresolved as of 2026-08, creating design uncertainty for cross-border payment products and loyalty/rewards features built on stablecoin balances.
Validator centralization during bootstrap. Tempo’s validator set at launch was drawn from its design partners (major fintechs and financial institutions) rather than being permissionless from day one, a common trade-off for payment-focused chains prioritizing early compliance and reliability over decentralization — a real, present-tense centralization risk during that bootstrap period, not yet resolved by a stated transition timeline in these sources.
Off-ramp/on-ramp compliance burden. Helius identifies “Regulatory Compliance” (KYC/KYB/AML), “Liquidity Sourcing,” “Messaging and Metadata,” and “Security” as the operationally hardest parts of a cross-border stablecoin flow — precisely the parts that happen off-chain and are not solved by faster blockchain settlement alone (Helius, “Solana’s Stablecoin Landscape,” as of 2025-05).
“Invisible integration” and consumer awareness. Helius predicts the future of stablecoin payments is “less about dedicated ‘stablecoin apps’ and more about the invisible integration of stablecoin technology into the familiar applications users already trust” (Helius, “Stablecoin Payments Guide,” as of 2025) — a design goal, but one in tension with consumer-protection goals that assume users understand what asset and issuer risk sits behind a payment they don’t realize is a stablecoin at all.

7. Open problems

Will GENIUS’s rulemaking deadlines hold? Paradigm’s own tracker frames this as likely to slip based on the Dodd-Frank precedent; the practical rules governing reserves, foreign issuers, and rewards were still being written as of 2026-08.
How should stablecoin rewards be regulated? The transaction-only vs. holding-based rewards debate (see /stablecoins/pegs-and-psm/) remains an active legislative fight with direct consequences for whether payment-focused stablecoin products can compete with card rewards programs.
Permissioned-to-permissionless transitions. Whether payment-focused chains like Tempo, or permissioned networks like Spherenet, can credibly deliver on eventual permissionless/decentralized operation, versus remaining consortium-governed indefinitely, is an open trust question not resolved by design documents alone.
Disclosure vs. seamlessness. Helius’s vision of stablecoins disappearing invisibly into everyday apps optimizes for adoption friction but raises an unresolved tension with regulatory goals (transparency about what asset a user holds and which issuer’s solvency they depend on) that these sources do not reconcile.

8. Ethereum vs Solana

Aspect	Ethereum (and Tempo)	Solana
Purpose-built payment chain	Tempo — independent EVM L1, sub-second finality, stablecoin-denominated fees	No dedicated payments-only chain; Solana mainnet itself serves this role
Point-of-sale payment standard	No single dominant standard in these sources	Solana Pay — QR-code/URL standard with Transfer and Transaction Requests
Peer-to-peer settlement cost/speed	Tempo targets sub-second finality, stablecoin-only fees; Ethereum mainnet itself is gas-cost-variable	<$0.01, ~400ms finality on Solana mainnet (Helius, as of 2025-05)
Permissioned enterprise rail	Tempo (bootstrap validators from design partners)	Spherenet (Sphere + Anza, modified SVM)
Regulatory anchor	GENIUS Act (federal, U.S.) applies across both chains for U.S.-issued payment stablecoins	Same GENIUS Act framework applies; chain choice doesn’t change issuer regulation

The more interesting comparison for payments is not really “Ethereum vs. Solana” but “general-purpose chain vs. purpose-built payment chain”: Solana’s general-purpose mainnet is already fast and cheap enough to support Solana Pay’s point-of-sale use case without a dedicated payments chain, while Ethereum’s higher gas costs and variable confirmation times are part of why Stripe and Paradigm built Tempo as a separate, payments-optimized layer-1 rather than routing payment volume through Ethereum mainnet or a general-purpose L2. Both ecosystems converge on the same regulatory anchor (GENIUS) and the same operational bottleneck (compliant on/off-ramps), regardless of which chain settles the value in between.

9. Reference doc

The reference

Tempo: The Blockchain Designed for Payments — Matt Huang (Paradigm), 2025-09-04. paradigm.xyz/writing/tempo-payments-first-blockchain

Summary of the reference

This short announcement post introduces Tempo as “a payments-first blockchain incubated by Stripe and Paradigm.” It frames the motivation as a gap in existing crypto infrastructure: “much of today’s crypto stack either explicitly or implicitly caters to trading (a highly valuable use case in its own right) but is comparatively underoptimized for payments.” Tempo is positioned as combining “Stripe’s experience in global payments and Paradigm’s expertise in crypto tech,” with design input explicitly credited to a wide set of non-crypto-native partners: “Anthropic, Coupang, Deutsche Bank, DoorDash, Lead Bank, Mercury, Nubank, OpenAI, Revolut, Shopify, Standard Chartered, Visa, and more.”

The post lists intended use cases broadly rather than narrowly: “global payments and payroll, remittances, tokenized deposits for 24/7 settlement, embedded financial accounts, microtransactions, agentic payments, and more” — deliberately spanning consumer, enterprise, and machine-to-machine (“agentic”) payment scenarios rather than positioning Tempo as solving only one of them. Organizationally, the post describes Tempo as “a new company with its own full-time team, jointly incubated by Stripe and Paradigm,” with author Matt Huang leading Tempo while continuing to lead Paradigm. The post frames this kind of incubation as rare for Paradigm, reserved for moments where the firm sees an opportunity to “help the crypto industry meet this moment of stablecoin adoption,” and explicitly positions Tempo as complementary to, not competitive with, existing crypto infrastructure — “a conduit for many large enterprises to come onchain.”

Notably, the post contains no technical architecture details (consensus mechanism, throughput figures, fee design) — those details in §3 above are drawn from later, secondary industry reporting rather than this announcement itself, which is intentionally a business/positioning piece rather than a technical specification.

Key quotes

“Tempo is purpose-built for stablecoins and real-world payments, born from Stripe’s experience in global payments and Paradigm’s expertise in crypto tech.” (Body)

“Much of today’s crypto stack either explicitly or implicitly caters to trading… but is comparatively underoptimized for payments.” (Body)

“We are excited to further crypto’s ability to tackle real-world use cases including global payments and payroll, remittances, tokenized deposits for 24/7 settlement, embedded financial accounts, microtransactions, agentic payments, and more.” (Body)

“We believe Tempo will complement existing crypto infrastructure and be a conduit for many large enterprises to come onchain, increasing adoption of crypto tools and infrastructure.” (Body)

How to read the original

Background needed: what distinguishes a general-purpose smart-contract chain (optimized for trading/DeFi composability) from a payments-optimized chain (optimized for settlement finality, fee predictability, and compliance hooks); no prior stablecoin-specific background is strictly required since the post itself is written for a general audience. Nothing needs to be skipped — the post is short (under 350 words) and every paragraph is load-bearing for understanding the announcement’s framing. The hardest part to read correctly is what the post does not say: it announces intent and partners but gives no technical specification, so treat it as a positioning document, not an engineering reference — the architecture details in §3 come from later reporting, not this piece.

What changed since

Tempo’s technical architecture (Reth execution client, Simplex Consensus via Commonware, stablecoin-denominated fees, no native volatile gas token, TIP-20 token standard) was disclosed in later technical announcements and industry reporting, not in this initial post.
Tempo launched mainnet in March 2026, roughly six months after this announcement, with an initial permissioned validator set drawn from design partners and a stated (but unverified in these sources) path to permissionless validation.
The GENIUS Act’s rulemaking process (§3, §6, §7) has continued to develop since this post, directly shaping the regulatory environment Tempo and similar payment chains operate within.

Secondary references

Helius, “Solana Pay: All You Need To Know” (below) — read for the point-of-sale/QR-code payment standard already live on a general-purpose chain, as a contrast to Tempo’s purpose-built approach.
Paradigm, “The Future of Payments Includes Stablecoins” (2023-07-26) — read for the earlier policy argument (reserve standards, competition, innovation) that pre-dates and helped motivate both Tempo and the GENIUS Act.
/stablecoins/pegs-and-psm/ — read for the fuller treatment of the stablecoin-rewards regulatory fight this page only summarizes.

The reference

Solana Pay: All You Need To Know — Helius, n.d. (fetched via WebFetch, 2026-08-29). helius.dev/blog/solana-pay

Summary of the reference

This guide documents Solana Pay as “a standard protocol & set of reference implementations that enable decentralised payments.” Its core technical contribution is a URL scheme that any wallet can parse: a Transfer Request encodes “a non-interactive request for a transfer of SOL or SPL Tokens,” while acknowledging the protocol is more expansive than simple transfers — “almost any Solana transaction can be converted into a valid Solana Pay URL,” which is the basis for the more general Transaction Request format capable of encoding arbitrary smart-contract interactions.

The guide enumerates the URL’s parameters: recipient (public key), amount, an optional SPL token mint for non-SOL payments, a reference field for unique transaction identification (the field used for reconciliation in this page’s §2 walkthrough), a label (merchant/app name), a message (contextual detail), and a memo (an on-chain note the guide cautions “should avoid sensitive data” since it is public). It explains the QR-code integration as the primary point-of-sale mechanism: URLs “convert into scannable QR codes, allowing users to initiate transactions without wallet connection,” which “removes the barrier of needed to connect your wallet to interact” — framing this as the key merchant-friction reduction versus a typical dApp flow that requires a full wallet-connect handshake before every interaction.

Key quotes

“Solana Pay is a standard protocol & set of reference implementations that enable decentralised payments.” (What Is Solana Pay?)

“A non-interactive request for a transfer of SOL or SPL Tokens.” (Technical Architecture, Transfer Requests)

“Almost any Solana transaction can be converted into a valid Solana Pay URL.” (Technical Architecture)

“[QR codes remove] the barrier of needed to connect your wallet to interact.” (QR Code Integration)

How to read the original

Background needed: the basic idea of a URL scheme/deep link (like mailto: or tel: links) that an app can parse into a pre-filled action, and what an SPL token mint address is (see /foundations/token-standards/). Nothing substantial needs to be skipped in a guide this focused. The hardest part to read correctly is the distinction between Transfer Requests and Transaction Requests: it is tempting to treat Solana Pay as “just a payment link,” but the Transaction Request format means a Solana Pay QR code can, in principle, trigger any on-chain program call a merchant wants — payment is the common case, not the only one.

What changed since

This guide’s summary notes it “contains no adoption statistics or dates” — later Helius material (e.g., “Solana’s Stablecoin Landscape,” cited throughout this page) provides the adoption figures (transaction volume, active addresses) this earlier protocol guide lacks.
Sphere’s SpherePay/SphereNet and similar off-ramp-focused products (§5 above) have since built additional infrastructure around the basic Solana Pay URL scheme for regulated, cross-border settlement use cases not covered in this guide.

Secondary references

Tempo (above) — read for the purpose-built-chain alternative to running payments on a general-purpose chain like Solana.
Helius, “Stablecoin Payments Guide for Fintechs & Financial Institutions” — read for the cost/speed comparison data used in §3–§4 above.
/stablecoins/fiat-backed-and-cctp/ — read for the “stablecoin sandwich” cross-border pattern Solana Pay and off-ramp partners plug into.

10. Sources

Solana Pay: All You Need To Know — Helius — fetched 2026-08-29 — https://www.helius.dev/blog/solana-pay
Tempo: The Blockchain Designed for Payments — Matt Huang, Paradigm — 2025-09-04 — https://www.paradigm.xyz/writing/tempo-payments-first-blockchain
The Future of Payments Includes Stablecoins — Brendan Malone, Paradigm — 2023-07-26 — https://www.paradigm.xyz/writing/the-future-of-payments-includes-stablecoins
The GENIUS Act Passed - Now the Real Work Begins — Katie Biber, Alex Grieve, Paradigm — 2025-07-29 — https://www.paradigm.xyz/writing/the-genius-act-passed-now-the-real-work-begins
An Interactive Guide to GENIUS Implementation — Madison Parker, Stefan Schropp, Paradigm — 2026-04-08 — https://www.paradigm.xyz/writing/an-interactive-guide-to-genius-implementation
Stablecoin Payments Guide for Fintechs & Financial Institutions — Helius — n.d. — https://www.helius.dev/blog/stablecoin-payments
Solana’s Stablecoin Landscape — Helius — n.d. (~2025-05) — https://www.helius.dev/blog/solanas-stablecoin-landscape
Stripe and Paradigm Announce New Layer 1 Blockchain ‘Tempo’ — Unchained — 2025-09 — https://unchainedcrypto.com/stripe-and-paradigm-announce-new-layer-1-blockchain-tempo/
Deep Dive: What You Need to Know about Tempo — Stripe’s L1 Blockchain — Sam Boboev, Medium — 2026 — https://samboboev.medium.com/deep-dive-what-you-need-to-know-about-tempo-stripes-l1-blockchain-4f86a0b3a745