English for Fintech Integration Engineers: Open Banking, PSD2, and Payment API Vocabulary

Fintech integration work sits at the intersection of financial regulation and software engineering — and it has its own dense vocabulary in English. Whether you are on a discovery call with a UK bank, reviewing a payment flow with a product manager, or debugging a failed webhook, the right words help you sound credible and communicate precisely.

This post teaches the core English vocabulary for fintech integration — and, more importantly, how to use it in real conversations.

The Regulatory Layer: Open Banking and PSD2

Open banking is the practice of banks sharing customer financial data with authorised third parties through secure APIs — with the customer’s consent. In the UK, it is regulated by the Competition and Markets Authority (CMA) and built on a standard called the UK Open Banking Standard.

“We’re integrating with three UK banks through open banking. The customer authorises access once, and then we can pull transaction history for up to 90 days.”

PSD2 (Payment Services Directive 2) is the European Union regulation that mandated open banking and introduced strong customer authentication requirements. Even after Brexit, UK regulations remain closely aligned with PSD2.

“PSD2 changed the game for payment service providers in Europe. SCA is the most visible impact for end users.”

Strong customer authentication (SCA) is a security requirement that means a payment must be verified using at least two of three factors: something the user knows (PIN, password), something the user has (phone, card), or something the user is (biometrics).

“The checkout conversion rate dropped after we enabled SCA. We need to apply for a transaction risk analysis exemption for low-value payments.”

Notice that engineers apply for exemptions, enable SCA, and trigger the authentication flow.

Provider Roles: AISP and PISP

Two roles matter in open banking conversations. An AISP (Account Information Service Provider) is authorised to read account data — balances, transactions, categorisation. A PISP (Payment Initiation Service Provider) is authorised to initiate payments on behalf of the customer.

“We’re licensed as an AISP, which means we can access account data but we cannot initiate payments directly. For that, we’d need a PISP licence or a PISP partner.”

These acronyms are always spelled out in spoken English on technical calls. Say each letter: “A-I-S-P”, “P-I-S-P”.

Payment initiation describes the act of triggering a bank transfer on behalf of a user from within a third-party app — without requiring them to log in to their bank directly.

“Payment initiation lets customers pay directly from their bank account at checkout — no card number required. Conversion rates tend to be higher.”

Account aggregation is the process of pulling together transaction data from multiple bank accounts into a single view. It is the core feature most AISPs build.

“Our account aggregation layer normalises transaction data across 40+ banks into a unified schema.”

Technical Integration Vocabulary

Webhook settlement refers to the process of receiving and processing payment status notifications sent by a payment provider via HTTP webhook. Settlement means funds have moved.

“We got the webhook, but the settlement status was pending for over 24 hours. We had to poll the status endpoint as a fallback.”

An idempotency key is a unique identifier sent with a request to ensure that if the same request is sent multiple times (due to a retry), the payment is only processed once.

“Always include an idempotency key in payment initiation requests. If the network drops and we retry, we don’t want to double-charge the customer.”

This is a term you must know how to explain to non-technical stakeholders: “It’s a unique ID we attach to every payment request so the system knows it’s already been processed if we have to retry.”

Reconciliation is the process of matching transaction records in your system against records from the bank or payment provider to ensure they agree.

“The nightly reconciliation job flagged three mismatches. We need to investigate whether those are timing issues or genuine discrepancies.”

A chargeback occurs when a customer disputes a transaction and the card network reverses the payment, returning funds to the customer.

“Our chargeback rate spiked this month — it’s above the Stripe threshold. We need to tighten our fraud detection logic.”

Sandbox testing refers to testing against a simulated payment environment provided by a bank or payment provider, using test credentials and fake data.

“All integration work should be done in the sandbox first. Do not test against production accounts — ever.”

Phrases for Technical Calls and Reviews

Use these in integration discovery calls, sprint reviews, and incident discussions:

• “We’re currently in the sandbox phase. The plan is to go live with production credentials in sprint 12.”
• “Our SCA exemption covers transactions under £30. Anything above that triggers a redirect to the bank’s authorisation page.”
• “The webhook is firing correctly, but our consumer is not acknowledging it — we need to return a 200 within five seconds.”
• “Can you confirm whether your API supports idempotent retries on the payment initiation endpoint?”
• “We had a reconciliation discrepancy last night — it turned out to be a timezone issue in the timestamp parsing.”

Key Collocations

Practice

Find the API documentation for a real open banking provider (Yapily, TrueLayer, or Plaid work well). Read the section on payment initiation or account aggregation. Write three sentences explaining the authentication flow to a non-technical product manager — use SCA, redirect, and authorisation correctly. Then read them aloud, focusing on pronouncing the acronyms clearly: “S-C-A”, “P-S-D-two”.