Corporate card accounting integration: the API guide

The term covers four distinct building blocks that are worth keeping separate. The first is journal entry export: every card transaction (payment, top-up, foreign exchange fee) becomes an accounting line with the right account, the right VAT rate, the right counterparty. The second is bidirectional synchronization: the accounting software sends back approved cost allocations, payment approvals, and settlements. The third is webhooks: the card pushes events in real time (transaction authorized, limit reached, missing receipt) rather than waiting for an overnight import. The fourth is bank reconciliation: the charges debited from the corporate account are automatically matched to the journal entries generated on the expense side.

Many offerings sold as "integrated" only deliver the first block: a CSV or FEC file to download and re-import manually. That is useful, but it is not integration. The key question when evaluating any solution: ask whether the connector is natively bidirectional or relies on a third party (an iPaaS, a custom script). Market leaders (Pennylane, Sage, Cegid, Dext) now expose REST APIs and ready-made connectors for expense management^[2][3].

Four vendors cover most of the French accounting software landscape. They each take a different approach to integration, and your choice of connector determines the quality of the card-to-accounting data flow.

In practice, two architectures coexist. Either the expense management platform includes its own connector (Spendesk, Payhawk, and the Greenway corporate card push journal entries directly into Sage or Pennylane), or it routes through a unified API layer like Chift, which normalizes calls across multiple vendors^[6]. The first option delivers tighter integration; the second offers more flexibility if you switch accounting software. The right choice depends on whether your accounting stack is stable or in transition.

The gap between "weekly CSV export" and "real-time webhook" integration is larger than it appears. CSV imposes a cycle: wait for end of period, export, import, fix mapping errors. Webhooks invert the logic: each transaction pushes an event, the journal entry is pre-generated, and the accountant validates rather than keys. Across a fleet of several hundred cards, the difference translates into days shaved off month-end close.

Technically, a webhook is simply an HTTP POST triggered by an event on the issuer's side. The card notifies your software (or an intermediary) that a transaction has just been authorized, with its amount, merchant, currency, and cardholder. The software then creates a draft journal entry, assigns the expense account based on pre-defined rules, and waits for approval. On the security side, you verify the payload signature and stay idempotent: the same event received twice must never create two entries.

The generated journal entry is only half the job. The other half is bank reconciliation: matching the charges debited from the company's corporate account to the journal entries already posted in the accounting system. This final control ensures nothing slips through: not a fraud, not a duplicate, not a transaction still missing a receipt. Modern tools automate this by cross-referencing amount, description, transaction date and counterparty^[7].

For a corporate card, reconciliation has one specific wrinkle: expenses are incurred throughout the month but debited later, sometimes grouped into a single transaction (see deferred payment). Without a native integration, you have to manually match each grouped debit to the dozens of underlying transactions. With a connector that pushes journal entries as they occur, reconciliation shrinks to exception handling: you only review what did not match automatically.

From 1 September 2026, all companies established in France must receive electronic invoices, and large enterprises must issue them^[8]. PDF invoices sent by email will no longer be a valid B2B billing method. The rollout then continues: mandatory issuance for mid-market companies, then for SMBs and micro-businesses from 1 September 2027.

What does this mean for the corporate card? Quite a lot, as it turns out. Some card expenses generate a supplier invoice (subscriptions, equipment, services) that must flow through a certified e-invoicing platform (PDP) or the public portal (PPF). If your card and expense management software do not connect to the e-invoicing chain, you will have to manually reconstruct the link between the card payment, its invoice, and its journal entry. That is exactly the kind of silo the reform is designed to eliminate.

In practice, verify three things with your card issuer: the ability to attach a receipt to every transaction (the payment approval record), export in the format expected by your PDP (typically a structured format such as Factur-X / XML), and full traceability linking the transaction, the invoice, and the journal entry. Without these three links in the chain, e-invoicing compliance becomes external plumbing: costly and brittle.

Beyond connector lists, two questions consistently prove decisive. First: who owns the account mapping? If it lives on the card vendor's side, changing your chart of accounts becomes a negotiation. If it belongs to you, you stay in control of your entries. Second: is the API documented and open? A closed connector with no public documentation locks you in: you depend entirely on the vendor's roadmap for even minor changes.

On the CSR side, accounting integration also opens an angle few solutions exploit: automatically linking each expense to a line in your CSR accounting and CSRD reporting. A journal entry correctly categorized at source feeds your impact metrics (sustainable mobility, responsible procurement, travel carbon footprint) with no extra effort. The accounting silo and the CSR silo both come down when the data flows freely.

At Greenway, the corporate card feeds directly into a back office that exports to the major French accounting platforms, with configurable allocation rules and a receipt attached to every transaction. The goal is not to impose a workflow, but to disappear into yours: your accounts, your VAT rates, your chart of accounts.