Open banking & API integration · engineering partner
Open banking API integration,
engineered as a layer you own.
TrustChange engineers open banking API integration for EU-facing PSPs, EMIs, neobanks, banks and licensed VASPs. We build the provider adapters, the consent lifecycle, the SCA flows, the payment initiation path and the ledger reconciliation as bespoke code under your brand — not a SaaS licence with a per-call fee. You get a banking integration API layer your engineers can extend, your risk team can govern and your auditor can read.
- EU-based engineers
- PSD2-aware delivery
- Consent audit trail
- GDPR-aware storage
What "open banking integration" means here
Banking API integration without the aggregator lock-in
Most searches for open banking and API integration surface a single aggregator behind a licence. We keep aggregators as an option — one adapter among several — but engineer the layer above them so your product owns the integration surface. Adapters can be added, swapped or stacked without rewriting the product code that sits on top.
Deciding whether to build, wrap or replace an existing integration? Start with CTO advisory. Card and PSP rails sit on payment gateway engineering. Reconciliation detail lives on payment ledger & reconciliation development.
Subsystems
Three subsystems in every open banking API integration we build
Open banking is not one service. It is account information, payment initiation and a consent state machine that binds them. We build all three as one product, on one architecture, with one team accountable end to end.
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01
Account Information (AIS)
Aggregated read access to a customer's bank accounts — balances, transactions and account details across the banks and aggregators you choose.
- Consent capture & refresh
- Multi-bank aggregation
- Transaction normalisation
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02
Payment Initiation (PIS)
Initiate SEPA, SEPA Instant and domestic pay-by-bank transfers straight from your product, with status polling and reconciliation into your ledger.
- SCA redirect / decoupled / embedded
- Idempotent submission
- Status polling & webhooks
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03
Consent, tokens & lifecycle
The consent state machine your regulator expects — granted, refreshed, revoked, expired — with an audit trail per user, per bank, per scope.
- Consent versioning
- Token rotation & KMS storage
- Revocation & audit log
Stack
What sits behind a digital banking integration API
Eight layers, one system. Every layer names an owner, a control and a piece of audit evidence — nothing is left implied under the "open banking" label.
Delivery patterns and evidence: how we deliver. Wider platform view: fintech infrastructure. Enterprise app angle: fintech app development company.
| Layer | What we build |
|---|---|
| Provider adapters | Direct bank APIs and PSD2 aggregators (e.g. GoCardless, TrueLayer, Tink, Nordigen, Yapily, Salt Edge or equivalents in your region) One canonical shape per API family; a new provider is an adapter, not a rewrite. |
| Consent management | Consent capture flows, state store, refresh scheduler and revocation hooks Consent state is stored, versioned and re-checked before every call — never guessed. |
| SCA & auth | Strong customer authentication paths — redirect, decoupled and embedded — with exemption logic where permitted Advisers set the policy; the flow implements it and stores the evidence. |
| PIS submission | Idempotent payment initiation with retry, status polling, webhook ingest and reconciliation into the double-entry ledger Every submission carries a client-generated idempotency key and a signed request id. |
| Data model | Canonical account, balance and transaction schema across banks, with FX, fees and pending states resolved Downstream product code doesn't branch per bank — the model does. |
| Storage & retention | GDPR-aware storage of consent, transactions and tokens with retention rules per data class Data mapping and retention are configuration; deletion runs on schedule. |
| Observability & alerts | Per-provider latency, error and consent-drop dashboards, plus alerts on stuck payments and expired consents On-call sees which bank slowed down before support does. |
| Runtime & delivery | EU-hosted, CI/CD pipelines, secrets in a managed KMS, 24/7 on-call cover Your identity provider, your data regions, your access rules. |
Consent & payment path
From consent to a reconciled payment
Every open banking call in the integration goes through the same gates. Speed comes from tuning the pipeline, not from bypassing consent checks or short-cutting the audit log.
- 01
Onboard user
First run
The user chooses a bank; the product records the consent scope and the target account list.
- 02
SCA & consent
Redirect / decoupled
The user authenticates with their bank. Consent state, token and expiry land in the store with an audit entry.
- 03
AIS pull / PIS submit
On demand or scheduled
The product either reads accounts and transactions or initiates a payment against the current consent.
- 04
Status & reconciliation
Continuous
Payment status is polled and webhooks are ingested; every event posts to the ledger with an idempotency key.
- 05
Refresh or revoke
Lifecycle
Consent is refreshed before expiry or revoked on user action; every state change writes to the audit log.
Delivery
How we deliver banking API integration
Five steps, in this order. Open banking work runs inside the product backlog — no separate PSD2 phase bolted on before launch, no big-bang release of an untested consent layer.
- 01
Scoping
Weeks 1–2
We map providers, banks, target regions, consent policy and the risk you must stand behind. Output: a scope, a control map and a costed plan.
- 02
Architecture
Weeks 3–4
Adapter contracts, canonical data model, consent state machine, SCA policy and reconciliation flow written down first.
- 03
Build
Two-week sprints
Adapters, consent store, PIS submission and reconciliation ship in slices. Each merge runs tests, static checks and a dependency scan.
- 04
Hardening
Before cut-over
Contract tests per provider, load work, failure drills, replay against sandbox and a third-party review window before touching production.
- 05
Launch and run
Cutover + ongoing
Named engineers on 24/7 cover. Runbooks, dashboards and the audit bundle are handed to your team on day one.
Engagement
Four ways to buy an open banking API integration build
Same engineers, same standard. Only the commercial shape changes.
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Fixed-scope build
A defined integration at a fixed price and date. Best when providers and regions are settled.
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Dedicated team
A standing squad with a lead. Best for long roadmaps and new banks each quarter.
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Staff augmentation
Senior engineers inside your team. Best when you already own the plan and need PSD2 depth.
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CTO advisory
Architecture and buy-vs-build review before you commit. Best at the design stage.
Questions
FAQ: open banking API integration
Six answers up front on scope, off-the-shelf trade-offs, coverage, PSD2, wrap-vs-replace and support. Bring the rest to the call.
What does open banking API integration cover in a TrustChange engagement?
We engineer a bespoke, client-owned banking integration API layer for you — provider adapters, consent management, SCA flows, PIS submission, AIS aggregation, storage and reconciliation into your ledger. It ships as source code in your repositories, with the IP assigned to you. There is no per-transaction fee to TrustChange and no shared multi-tenant backend between you and your bank connections; commercial terms with the underlying providers stay directly with you.
How is your work different from an off-the-shelf open banking and API integration provider?
Off-the-shelf aggregators bundle bank access behind a licence and a fixed API. TrustChange keeps the aggregator model as an option but engineers the layer above it — consent lifecycle, SCA policy, ledger posting, retention — so your product owns the integration surface. You can swap or stack providers later without rewriting your product code. That trade-off is honest: a bespoke build takes longer up front, but banking integration lock-in is exactly what regulated operators want to avoid.
Which banks, regions and providers can the digital banking integration API cover?
Direct bank APIs and PSD2 aggregators in the EU, EEA and UK are the reference scope, with digital banking integration API adapters for the mainstream families used by PSPs, EMIs and neobanks. UK-specific work — a digital banking integration API UK integration under the OBIE-flavoured spec, for example — sits on the same adapter layer. Other regions land as new adapters against the same canonical model.
How does API integration in banking handle PSD2, SCA and GDPR in your builds?
TrustChange is an engineering partner, not a law firm — your compliance advisers and DPO set the policy; we ship the code and the evidence. That means PSD2-aware SCA flows with exemption logic where permitted, consent state that is versioned and revocable, token storage inside a managed KMS, GDPR-aware retention rules and an audit log that carries who, what, when and why for every call. Nothing about PSD2 licence status, opinions or regulator approvals is claimed on your behalf.
Do you replace our current banking API integration or wrap it?
Both patterns are common. Most engagements start by wrapping current providers behind the canonical model so nothing in production changes on day one, then add or swap adapters as the roadmap allows. That keeps working revenue live while the new open banking API integration takes shape underneath, and it avoids a big-bang cutover on a payment path.
Do you also run the integration after launch, or hand it over?
Both are on the table. Most clients start with named TrustChange engineers on 24/7 cover during the first months while their own team ramps up, then take the platform in-house with runbooks, dashboards and an on-call handover we author together. Some keep us on as a dedicated development team or on staff augmentation for new-provider and consent-model roadmap work.
Book a discovery call for open banking API integration
Bring the target banks, the regions, your consent policy and where the pressure sits — PIS latency, expiring consents, silent duplicates or a stuck reconciliation. We come back with a control map, an architecture view and a costed plan. No demo theatre.