Custom checkout
Custom checkout integrations demand a flexible architecture for development teams building native application interfaces. Merchants can leverage a custom payment API to transmit raw transaction data directly between servers while routing volumes across an international acquirer partner network.
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Cardflo's custom checkout solution provides merchants with complete control over their payment experience. Integrate our robust payment orchestration platform directly into your existing checkout flow, maintaining brand consistency and optimising the user journey for high-risk and enterprise operations.
Design every element to suit your specific business needs and customer expectations.
Cardflo's API-driven custom checkout provides direct access to our multi-acquirer network, enabling bespoke payment experiences and advanced SCA management. This flexibility allows for the optimisation of transaction lifecycles and significantly increases global approval ratios.
Custom checkout overview
A custom checkout implementation represents a direct integration where the merchant maintains full control over the presentation layer and data collection process at the point of sale.
Unlike hosted payment pages that redirect the user to a third-party environment, a custom framework utilise APIs or client-side SDKs to embed payment fields within the existing website architecture.
This approach allows enterprise merchants and those in specialised sectors to organise the payment flow according to specific operational requirements, such as custom data capture for AML compliance or niche vertical needs. By managing the user interface directly, businesses can minimise friction associated with external redirects and maintain visual consistency.
The technical stack typically involves a payment gateway or orchestrator that handles the transition of sensitive card data through tokenisation, ensuring the merchant environment stays within a manageable PCI DSS compliance scope while retaining total autonomy over the front-end behaviour.
How custom checkout works
Initial payload configuration
The merchant server initiates a request to the gateway to establish a transaction intent. This step defines the currency, amount, and required payment methods. A secure token or session identifier is returned, which the front-end application uses to initialise the custom components or direct API calls within the browser environment.
Secure data capture
Payment credentials, including the PAN, CVV, and expiry date, are entered into the merchant's custom-designed fields. To reduce PCI DSS burden, these fields often utilise vaulted elements or iframes that transmit data directly to the acquirer or vaulting service without sensitive information touching the merchant's primary servers.
Authentication and SCA
If the transaction falls under PSD2 mandates, the checkout logic triggers a 3DS challenge. For a custom integration, the merchant decides how the challenge window appears, ensuring the Strong Customer Authentication process is integrated into the site architecture rather than appearing as a disconnected pop-up that might deter completion.
Authorisation and response
The encrypted payload is sent to the acquirer for authorisation via the card schemes. The issuer returns a response code, such as '00' for approval or specific decline reasons. The custom checkout logic then dictates how to display this result to the customer, allowing for immediate retry logic if necessary.
Why custom checkout matters
Friction reduction and conversion
Redirecting customers to external domains frequently triggers security concerns or creates latency that leads to basket abandonment. A custom checkout keeps the user within the merchant's domain, which can positively impact conversion rates. This is particularly relevant for high-value transactions where brand trust and a consistent user experience are critical factors in the cardholder's decision to proceed with the authorisation.
Advanced risk and compliance
Custom integrations allow for the collection of additional data points beyond standard payment fields, such as specific KYB information or industry-specific metadata required for risk analysis. Merchants can tailor the data entry process to satisfy internal AML policies or to provide more context to issuers, potentially improving approval rates by reducing the likelihood of a transaction being flagged as suspicious during the authorisation stage.
Custom checkout use cases
Inventory-linked order authorisation
Retailers with scarce or configurable stock must reserve inventory, recalculate tax and confirm delivery options before submitting an authorisation, without exposing stale totals. Cardflo’s custom payment API lets backend services control request sequencing, idempotency keys and capture timing while routing eligible transactions through the acquirer partner network.
In-app native card entry
Product teams building iOS and Android applications may need card fields, validation messages and recovery paths to follow native design systems rather than webview behaviour. Cardflo provides API access for tokenisation and server-side payment requests, while development teams retain control of field rendering, decline handling and 3DS2 challenge presentation.
Bespoke onboarding payment steps
Regulated services may collect identity evidence, select an account tier and take an initial card payment within one conditional onboarding journey, with errors returned at different stages. Cardflo’s API supports server-to-server payment initiation and structured response handling, allowing product teams to map validation, SCA and issuer declines to specific interface states.
Delayed capture fulfilment flows
Made-to-order merchants often authorise a card when production begins but capture only after goods pass inspection or enter fulfilment, requiring precise control over authorisation validity and order status. Cardflo enables backend systems to initiate, reference and capture transactions through its acquirer partners, with custom logic for expiry, cancellation and partial fulfilment.
Custom checkout by the numbers
Typical figures observed by enterprise merchants when moving from a multi-redirect hosted page to an integrated, single-domain checkout experience.
An industry benchmark for well-optimised custom flows, compared to higher abandonment rates often seen when third-party redirects increase friction.
The relative increase in successful mobile transactions frequently reported after customising gestures and form-factor elements for small-screen users.
Methodology: these figures are illustrative ranges drawn from published industry data and observed merchant cohorts, not guarantees. Actual results depend on your risk profile, card mix, geography and acquiring setup, and are confirmed only in your own pricing and approval terms.
Related terms
Talk to our team about a live rollout across our acquirer partners' rails.
What you get with Custom checkout
- Full ownership of the user interface design and customer journey mapping.
- Elimination of third-party redirects to reduce mid-flow drop-off rates.
- Granular control over the placement and styling of payment input fields.
- Direct integration with internal CRM and inventory management systems via API.
- Ability to implement bespoke retry logic for soft decline recovery.
- Support for multi-language and multi-currency displays adapted for global markets.
- Collection of secondary metadata for enhanced fraud screening and risk profiling.
- Reduced PCI DSS scope through the use of secure field tokenisation.
- Customisable 3D Secure 2 authentication overlays for improved user experience.
- Flexibility to prioritise specific payment methods based on customer geolocations.
A short scoping call, then a written plan for your MIDs.
Questions about Custom checkout
How does a custom checkout affect my PCI DSS compliance requirements?
While a custom checkout gives you control over the UI, the level of PCI DSS compliance depends on how data is handled.
Using 'elements' or hosted fields allows sensitive details to be encrypted and sent directly to the PSP, which typically keeps you within the Scope of SAQ A-EP.
If your servers capture or transmit raw card data, you would fall under the more rigorous SAQ D requirements. Most modern custom integrations favour field-level tokenisation to minimise the compliance burden while allowing for front-end customisation.
Can I support multiple payment methods through a single custom integration?
Yes, a well-architected custom checkout uses a payment orchestration layer to manage various APMs, such as digital wallets, bank transfers, and local schemes, under a unified front-end. The merchant defines the logic for which methods appear based on the user's IP address, currency, or MCC.
This allows for a consistent look and feel across all payment types regardless of the secondary processors involved in the final settlement.
What is the impact of custom checkouts on mobile conversion rates?
Custom checkouts allow for responsive design that is specifically optimised for mobile viewports, avoiding the common layout shifts found in generic hosted pages.
By utilising mobile-specific features like biometric authentication and native digital wallet buttons within the custom flow, merchants can reduce the number of taps required for authorisation.
This is essential for minimising abandonment in mobile commerce where user patience for latency or complex form-filling is notably lower.
How should custom payment API integrations manage idempotency for duplicate requests?
Development teams should assign a unique idempotency key to each payment operation and retain it across retries caused by timeouts or uncertain responses. The merchant server should also store the relationship between its order reference, Cardflo transaction identifier and final payment state.
This prevents repeated API calls from creating unintended duplicate authorisations while allowing the original result to be retrieved or reconciled.
Is it possible to include bespoke fields for data collection?
One of the primary advantages of a custom checkout is the ability to collect non-payment data that assists with settlement and reconciliation. Merchants can add fields for VAT numbers, gift messages, or specific delivery instructions that are passed into the transaction's metadata.
This information can then be used by the acquirer for risk scoring or by the merchant's back-office for automated dunning and account reconciliation.
How do custom checkouts handle decline recovery differently than hosted pages?
Hosted pages often provide a generic error message for a decline. A custom checkout allows the merchant to interpret the specific decline reason code from the issuer and provide a tailored response.
For instance, if a 'soft decline' occurs due to a lack of 3DS authentication, the custom flow can immediately trigger the 3DS process without forcing the customer to re-enter their details, thereby saving the sale.
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