Integrating business systems with APIs

In many SMEs data still travels by hand: a file is exported from the e-commerce, pasted into the ERP, retyped into accounting. Every manual step is time lost and an opportunity for error. APIs — the interfaces that allow two pieces of software to talk to each other directly — serve precisely to break this cycle. It is not just a technical issue: it is organisation and data quality. Let’s see what they are, where to use them and what is needed to do it well.

What an API is, in practice

An API (Application Programming Interface) is the way a piece of software exposes its own data and functions to other software in a structured manner. Instead of downloading a file and re-importing it, system A asks system B for the data it needs, or sends it to it, automatically and in real time.

The classic example: when an order arrives on your site, an integration via API creates the customer in the ERP, updates the warehouse and generates the invoice, without anyone touching the keyboard. The value is not the technology in itself, but the elimination of double entry and the errors that result from it.

Where it creates most value in an SME

The most useful integrations are those that connect systems that today work in isolation.

• E-commerce → ERP: orders, customers and stock aligned without manual intervention.
• ERP → accounting: issued and received invoices flow into the accounting system already categorised.
• Bank → accounting: statements arrive automatically and payment reconciliation becomes almost immediate (via standards like CAMT / ISO 20022, used by Swiss banks).
• CRM → invoicing: when a quote becomes an order, the data passes without re-entry.
• Internal systems → reporting tools: the data flows into up-to-date dashboards.

The rule for setting priority is simple: integrate the high-volume, high-repetition flows first. That is where the time saved pays back the project.

How an integration is built

There are three routes, of increasing complexity.

1. Ready-made connectors: many software packages offer native integrations or marketplaces. It is the fastest and cheapest route when the connector for your two systems exists.
2. Automation platforms (iPaaS-type): tools that connect different applications with configurable logic without writing code. Excellent for standard flows.
3. Custom development: when specific logic is needed or the systems do not have ready-made connectors, the integration is built on the available APIs.

Before choosing, always check that both software packages expose an adequate and well-documented API. A closed system, without an API, is a constraint that must be weighed already at the purchase stage.

Security and data protection

Connecting systems means making data travel, often personal data. Here attention is not optional.

• Authentication: APIs must be protected with keys or tokens; credentials are not shared and not left in clear text.
• Encryption: data in transit must travel encrypted.
• Minimum necessary: only the data needed for the flow is exchanged, not the entire archive.
• Data protection: if an integration transfers personal data to a foreign provider, the obligations of the new Swiss Federal Act on Data Protection (nFADP) must be respected, including the question of where the data is stored and processed.

A poorly protected integration exposes company and customer data: convenience must never come before security.

The cost and how to assess it

An integration has a cost of implementation and one of maintenance — APIs change, systems are updated. The correct assessment is to compare it with the current cost of manual work: how many hours a month are spent moving data, and how much the resulting errors cost (wrong invoices, misaligned warehouse, avoidable reminders). In most cases, on high-volume flows, the return is quick.

Mistakes to avoid

• Integrating everything at once instead of starting from the most burdensome flow.
• Not providing for error handling: what happens if a piece of data does not pass? An alert is needed, not silence.
• Neglecting maintenance, treating the integration as a “once and done” project.
• Ignoring the quality of the source data: connecting two dirty archives only propagates errors faster.

How we work

SIH ONE is an AI-native fiduciary group: we combine technological expertise on integrations with knowledge of Swiss accounting and tax processes. This allows us to design connections between your systems that respect local banking and accounting standards and data protection, with concrete attention to the return on investment.

Want to make your systems talk to each other and eliminate double entry? Let’s talk about it together.