Integrating Exact Online With Your Own Software: When, How and What It Costs

Introduction

For many Dutch businesses, Exact Online is the financial backbone. At the same time, those same businesses often run their own software alongside it: a webshop, a customer portal, a planning tool or an internal system. The moment those two worlds do not talk to each other, the familiar pattern emerges of double entry, manual retyping and reconciliation differences at month-end close.

An integration between your own software and Exact Online solves that, but it is not a switch you simply flip. In this guide we explain when an integration is worth it, what is technically possible, where it gets hard and roughly what it costs. We write this from experience; our page on the Exact Online integration covers the technical approach in even more depth.

When an Exact Online integration is worth it

The clearest signals are operational. Someone creates an order in your system and then manually retypes that same order into Exact. Or finance waits every month for exports from different tools to reconcile the books. Or customers call to ask whether their invoice has been paid, while that information is readily available in Exact. Each of these is a moment where an integration removes time and errors.

The value of an integration is usually more than time savings. Real-time insight into outstanding invoices and cash flow helps with steering, and an automated integration produces an auditable trail of every entry. For sectors with tight margins, like wholesale or e-commerce, the difference between manual and automated translates directly into operations.

What you can do with the API

Exact Online exposes a comprehensive REST API that lets you read and write almost every entity: sales orders, draft invoices, purchase invoices, general ledger accounts, relations and project entries. In practice this means an order in your system can automatically become a sales entry or draft invoice in Exact, and payment statuses can flow back to your own application or customer portal.

For real-time behaviour we use webhooks where possible, so your application knows within seconds that something has changed. Where webhooks are not available, we supplement with scheduled synchronisation that only processes differences. If you are still building the application itself, our page on having a web application built is a logical starting point.

The three things that make an Exact integration hard

"The integration itself is rarely the hard part. The hard part is getting the accounting logic around it right."

— Sidney de Geus, co-founder MG Software

First, authentication. Exact uses OAuth 2.0, with access tokens that expire and refresh tokens that must be renewed periodically. If that token rotation is not built as a reliable background process, the integration will stall sooner or later at an inconvenient moment. We build that rotation in automatically so an expired session never becomes the problem.

Second, the administrations, called divisions in Exact. Many organisations manage multiple legal entities or branches in separate divisions, and every API call must explicitly name the correct administration. Third, ledger mapping: how an order translates into ledger lines differs per company and requires close collaboration with your finance team. And finally, Exact’s rate limits are more restrictive than many teams expect, especially when importing historical data.

What an integration costs and how long it takes

A first production integration with a defined goal, for example sales orders that land as draft invoices in Exact, usually fits within a few sprints. The price within that scope depends on the number of entities you want to synchronise, the complexity of the ledger mapping and whether a test environment is available.

For organisations with multiple administrations, complex mapping or high volumes, we recommend a phased approach where each phase delivers a working and testable result. That avoids a long project without interim value. For a first range you can use our calculator, and on the page about software integrations you can read how we approach integrations in general.

Common mistakes

The most common mistake is trying to synchronise everything at once. An integration that covers orders, invoices, stock, relations and projects in one go is hard to test and hard to maintain. Start small, with the flow that costs the most manual time, and then expand based on what proves to work in production.

A second classic is ignoring error handling. An API call can fail due to a timeout, a rate limit or temporary unavailability. Without idempotent requests and a proper queue for failed mutations, you get duplicate entries or silent data errors. Those are exactly the kind of errors that only surface at month-end close, when they are most expensive to investigate.

How we approach it

We start with a short discovery in which we determine together which Exact entities are relevant, in which direction data flows and which accounting rules apply. We then set up OAuth 2.0 securely, with encrypted token storage and automatic rotation, and develop against an Exact test administration so we never experiment with production data.

Every mutation is built to be idempotent, failed requests land in a queue with full context, and we actively monitor the integration after go-live. Because Exact regularly makes API changes, we build an abstraction layer that isolates such changes, so an Exact update does not touch your entire integration.

Conclusion

An Exact Online integration is not a technical trick, but an investment that structurally removes manual work and errors. The success is not in the API itself, but in the care around authentication, administrations, ledger mapping and error handling. Start small, build reliably, and expand based on what works.

Want your own software to talk to Exact Online? Get in touch with MG Software or first review our detailed page on the Exact Online integration. We map your process and build an integration that holds up at month-end close too.