Integration service

Payment gateway integration service: any gateway with an API, connected once, used by every checkout.

Every processor has an API and every integration is the same list of things done slightly differently: authenticate, tokenise, authorise, handle 3-D Secure, capture, refund, listen for notifications, reconcile. We do that list for gateways our merchants and partners bring, on our side, so the merchant's store never has to. This page says what the service covers, how it runs and what it does not include.

Gateways already connected →

What an integration covers

Authentication. API keys, HMAC-signed requests, OAuth, mutual TLS, whatever the gateway uses, held encrypted per merchant.
Card capture. The gateway's hosted fields or components so card data stays out of scope, or a tokenisation flow where that is the model.
Authorise, capture, void, refund. Including partial captures and partial refunds from the merchant's console.
3-D Secure. Redirect or challenge flows, result codes mapped to retry-or-stop decisions.
Local and alternative methods. iDEAL, Bancontact, SEPA, Interac, PIX, wallets and buy-now-pay-later where the gateway exposes them.
Notifications. Webhooks where they exist; scheduled polling where they do not, including refunds and chargebacks arriving days later.
Reconciliation. Every event matched to a payment and an order; a ledger per merchant.
Idempotency and retries. No double charges across routes or retries.

For merchants and for providers

Merchants

You were approved by a processor your platform does not list. We integrate it once and put it behind your checkout, with a second route if you have one. Custom gateway on Shopify.

Gateways and PSPs

You want your API available to merchants on Shopify and WooCommerce. We integrate it as a partner gateway and every merchant you onboard uses it. Partner program.

How it runs

Documentation review. We read the API reference and write down the integration shape: flows, edge cases, what the docs leave out.
Sandbox build. Connection built and tested against the gateway's test environment with its test cards and simulated failures.
Certification where the gateway requires one.
Live cutover. Production credentials, one live order per method, refunds tested, notifications confirmed.
Maintenance. API changes tracked; the integration is ours to keep working.

Gateways with a documented REST API and hosted fields typically take days. Gateways with unusual flows, no sandbox or notification gaps are scoped first and quoted in the conversation.

What it does not include

Opening the merchant account. You apply to the gateway; approval is theirs.
Building a Shopify payments app. The gateway runs behind an own-domain checkout, not inside Shopify's.
Holding or settling funds.
Advice on the gateway's terms or on your platform's terms.

Frequent questions

Which payment gateways can you integrate?

Any gateway with a documented API: NMI, Nuvei, Airwallex, Checkout.com, PXP, Adyen, Whop, regional acquirers, crypto rails, and custom endpoints.

How long does a gateway integration take?

Days for a gateway with a documented REST API and hosted fields; longer when flows are unusual or a certification is required. You get a timeline before work starts.

Do you charge per integration?

Merchant plans are on the pricing page. Partner integrations are agreed in conversation.

Does the integration live in my store?

No. It lives on the hosted checkout, so your store never handles gateway calls or card data.

Send the gateway's API documentation and a sandbox login.

You get a written integration shape and a timeline before any work starts.

Integrations →

Integrations → · Partner program → · Custom gateway on Shopify → · Custom gateway on WooCommerce →

CascadeCheckout is checkout software, not a payment service provider, bank or merchant-account seller. You contract with your own gateway or acquirer, disclose your real business category to them, and receive payouts from them. We never hold funds and we do not promise that any processor will approve you.