NoxPos Whitepaper
Non-custodial stablecoin checkout for merchants — architecture, direct-pay settlement, multi-chain settlement, and the NoxPos product ecosystem.
Executive summary
NoxPos is a non-custodial stablecoin checkout platform for merchants worldwide. Customers pay stablecoins — USDT on TRON, USDC on Base, USDC + USDT on Solana; funds settle directly to merchant-controlled wallets — never through a NoxPos custodial pool.
The platform serves brick-and-mortar stores (Cashier POS) and store/developer integrations (WooCommerce, Hosted Pay Page, Pay Button SDK, and Shopify when approved). Two fee models apply: the Cashier collects a platform service fee off-chain (0.5% free tier, 0.4% for VIP subscribers) while customers pay merchant wallets in full; store plugins and Hosted/SDK checkouts also use direct pay to the merchant wallet and charge a flat 0.3% off-chain via prepaid balance or monthly settlement — independent of Cashier VIP.
Problem & vision
Traditional card rails impose FX volatility, chargebacks, multi-day settlement, and high cross-border fees. Custodial crypto gateways introduce counterparty risk — merchants must trust a third party to hold and release funds.
NoxPos vision: every payment lands directly with the merchant. We provide checkout UX, chain reconciliation, and store integrations — but we never hold merchant assets or customer keys.
- Instant stablecoin settlement (seconds, not days)
- No FX exposure when pricing in USD-pegged stablecoins
- Auditable on-chain payment trails per order
- Borderless checkout for global customers
Non-custodial architecture
NoxPos operates public surfaces including noxpospay.com (merchant accounts & marketing), app.noxpospay.com (Integration API, Cashier backend, Hosted Pay / wallet-pay pages), and pay.noxpospay.com (customer payment surfaces where applicable). Merchant receiving addresses are configured by the merchant — under Profile → Plugin configuration for WooCommerce / Hosted / SDK, Cashier receiving wallets, or per-session overrides — not held in escrow by NoxPos.
| Layer | Role |
|---|---|
| Checkout UI | QR modal, network tabs, countdown (WooCommerce / SDK / Hosted / Shopify pay page) |
| Hosted pay page | app.noxpospay.com/hosted-pay/… — wallet connect & direct transfer confirm |
| Settlement | Customer pays merchant wallet in full (direct pay) |
| Reconcile API | Chain polling matches invoice amount + tx hash → order fulfillment + off-chain 0.3% fee |
| Merchant wallet | Non-custodial address controlled by merchant |
Direct-pay settlement
Cashier and integration checkouts use direct pay: the customer transfers the locked stablecoin amount to the merchant’s receiving address. NoxPos reconciles the on-chain transfer, marks the order/session paid, and bills the platform fee off-chain (Cashier VIP/free tier rates, or a flat 0.3% for store plugins / Hosted / SDK) from the merchant’s prepaid balance or monthly settlement account.
| Chain | Token | Payment mode |
|---|---|---|
| TRON | USDT (TRC20) | Direct transfer to merchant address |
| Base | USDC (ERC20) | Direct transfer to merchant address |
| Solana | USDC + USDT (SPL) | Direct transfer to merchant address |
Always pay the exact amount shown on the QR (including the unique suffix). Wrong amount or wrong address will not complete the order.
Product ecosystem
- Store plugins and Hosted/SDK share the same modal design spec and reconcile rails
- Integration API Key generated at noxpospay.com/profile (server-side only)
- Unique micro-suffix on invoice amounts prevents payment collisions
| Product | Audience | Status |
|---|---|---|
| NoxPos POS | Brick-and-mortar stores, terminals, catalog | Live — app.noxpospay.com |
| WooCommerce Gateway | WordPress / WooCommerce merchants | Live — v0.1.65 |
| Hosted Pay Page | Any stack — redirect / invoice / landing checkout | Live — v0.1.0.0 |
| Shopify App | Shopify stores | Coming soon |
| Pay Button SDK | Developers, SaaS, custom storefronts | Live — v0.2.1.0 |
Integration API
Third-party integrations authenticate with a Bearer API key (noxpos_…). The verify endpoint confirms the key, wallets, and fee account; session endpoints register checkout context; reconcile endpoints poll on-chain transfers and, on match, mark the order/session paid and charge the 0.3% platform fee off-chain.
| Endpoint | Purpose |
|---|---|
| POST /api/integrations/verify | Validate API key, return wallets + fee account + platformFeeBps |
| POST /api/integrations/sessions | Register plugin session + notifyUrl for HMAC settlement push |
| POST /api/integrations/hosted-pay/sessions | Create Hosted Pay session → payUrl redirect |
| POST /api/integrations/reconcile | Match on-chain transfer → fee + settlement notify |
| GET /api/exchange-rates | Fiat → stablecoin conversion for non-USD carts |
Fee model
The Cashier POS uses direct-pay: customers pay the merchant wallet in full, and NoxPos collects a platform service fee off-chain (0.5% on the free tier, 0.4% for VIP subscribers) via prepay balance or monthly settlement. During the trial window advertised at signup, Cashier platform service fee may not apply.
WooCommerce, Hosted Pay, Pay Button SDK, and other store-plugin checkouts also use direct-pay to the merchant wallet. The integration platform fee is a flat 0.3% (30 basis points) per successful order, billed off-chain from the shared prepaid balance or monthly settlement — not tied to Cashier VIP, and not deducted from the customer’s on-chain payment.
Shopify merchants may additionally pay Shopify's third-party payment transaction fee (0.2%–2.0% by plan) because crypto checkout is an external gateway — separate from NoxPos's 0.3% fee. WooCommerce has no marketplace surcharge beyond the 0.3% NoxPos fee.
| Fee | Rate | Collected by |
|---|---|---|
| Cashier platform fee (free tier) | 0.5% | Off-chain — prepay / monthly settlement |
| Cashier platform fee (VIP) | 0.4% | Off-chain — prepay / monthly settlement |
| Plugin / Hosted / SDK platform fee | 0.3% | Off-chain — prepay / monthly settlement |
| Shopify third-party fee (if applicable) | 0.2%–2.0% | Shopify billing |
| Card processing | N/A | Crypto checkout — no card rails |
Security principles
- Non-custodial by design — NoxPos never holds merchant order funds
- API keys server-side only; never embedded in browser checkout JS
- QR checkout with exact amount suffix — customers must pay the locked amount to the merchant address shown
- Reconcile matches amount, merchant address, and time window before fulfillment
- Merchant wallet private keys never touch NoxPos systems — addresses only
- Hosted allowlists and redirect checks reduce open-redirect risk on Hosted Pay return URLs
Roadmap
- Shopify Payments Platform partner approval → native checkout payment method
- Profile wallet sync for OAuth-connected store apps
- Magento module and expanded regional stablecoin support
- Enhanced merchant analytics and multi-store reporting
Contact & resources
- Website: https://noxpospay.com
- Terms of Service: https://noxpospay.com/terms
- Privacy Policy: https://noxpospay.com/privacy
- Documentation: /docs/woocommerce · /docs/hosted-pay · /docs/shopify-app · /docs/pay-button-sdk · /docs/cashier · /docs/guide
- Technical support: footer link on noxpospay.com
- Integration API Key: https://noxpospay.com/profile