Welcome to 4xx.io

Paymentsinfrastructurefor global commerce

One API for cards, Open Banking, and Faster Payments. Multi-provider routing through Stripe, Adyen, and more — with real-time reconciliation and built-in compliance baked in from day one.

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99.97%Uptime SLA

<120msAvg. processing latency

FCA readyCompliance framework

4+Payment rails

Create a payment intent

POST https://api.4xx.io/v1/payment-intents
Idempotency-Key: order_7f3a29bc
Authorization: Bearer sk_live_•••••••••••••

{
  "amount": 15000,       // £150.00 in pence
  "currency": "GBP",
  "method": "open_banking",
  "merchant_id": "mch_9e4f1a"
}

// Response
{
  "id": "pi_4xx_8b2c6d91",
  "status": "created",
  "provider": "open_banking",
  "redirect_url": "https://auth.4xx.io/ob/8b2c6d91"
}

Core platform

Every layer of
the payment stack

From payment intent creation to ledger reconciliation — built as a cohesive system, not bolted-together services.

Smart provider routing

Intelligent fallback across Stripe, Adyen, Open Banking, and Faster Payments. Route by cost, success rate, or method — automatically.

Real-time reconciliation

Double-entry ledger with automated daily reconciliation. Spot discrepancies before they become problems.

Risk & fraud scoring

Per-transaction risk scoring with configurable rule engine. Block, flag, or challenge suspicious activity in real time.

Signed webhooks & event streams

HMAC-signed webhook delivery with automatic retries, replay, and per-endpoint filtering. Never miss a payment event.

Dispute management

Track, respond, and win chargebacks. Evidence collection and submission workflows built into the API.

Idempotent by design

Every mutation requires an idempotency key. Safe retries, zero duplicate charges — guaranteed.

Integrations

Four rails, one API

Abstract away provider complexity. Switch or combine payment methods without changing your integration.

Stripe

Card payments, 3DS2, subscription billing, and global acquiring via Stripe's network.

Cards3DS2Subscriptions

Adyen

Enterprise card acquiring, international payment methods, and unified commerce.

EnterpriseGlobalUnified

Open Banking

Account-to-account payments via Open Banking rails worldwide. Lower fees, instant settlement, no card network.

FCA regulatedInstantLow cost

Instant Bank Transfers

Near-instant bank transfers across UK Faster Payments, SEPA Instant, FedNow and more — operational 24/7, 365 days a year.

24/7Multi-currencyBank transfer

Wallets supported

Apple PayGoogle PayPayPalClick to PaySamsung PayAmazon PayLink

Available through any card-processing rail (Stripe, Adyen, Checkout.com, Worldpay) — one integration, all wallets.

Compliance & security

Regulated from
the ground up

Global payments come with strict regulatory requirements. 4xx.io ships with KYB workflows, AML screening, PCI-DSS data handling, and a full audit trail — so you don't have to build compliance from scratch.

KYB onboardingBusiness verification and document collection built into the merchant onboarding flow
AML & sanctions screeningAutomated screening against global sanctions lists (OFAC, UK, EU, UN) on every merchant and transaction
Full audit trailImmutable, timestamped event log for every state transition — ready for regulatory inspection
PCI-DSS scope reductionCard data never touches your servers — handled by certified tokenisation on the provider side

Pricing

Simple, transparent pricing

No setup fees. No monthly minimums. Pay for what you process.

Starter

1.4% + 20p

Per card transaction (EU cards). Open Banking from 0.1%.

All payment rails
Real-time webhooks
Basic reconciliation
Email support

Get started

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