Fortnox is the most widely used accounting system in Sweden. If you’re building a fintech, SaaS, or bank product, chances are you’ll need to connect to Fortnox data sooner or later. The question is: do you build that integration yourself, or do you buy into a platform that already solved it?

Let’s break it down.

The Challenge of Building Directly Against Fortnox

At first glance, connecting to Fortnox might seem straightforward. It’s “just another API.” But the reality often looks different once you get into production:

• Long development cycles – Authentication flows, OAuth scopes, token refresh, and rate limits all add complexity before you even start pulling business data.
• Constant updates – API versions change, endpoints evolve, and you’ll need to keep your integration compliant.
• Single system only – Even if you manage to nail the Fortnox integration, your customers don’t all use Fortnox. Some will be on Visma, Björn Lundén, Tripletex, or others. That means you’re back to square one each time.

The hidden cost isn’t just developer time. It’s also opportunity cost—delayed launches, frustrated customers, and the ongoing maintenance burden.

The Alternative: One API, Many Systems

Instead of going system by system, API.1 from Zwapgrid offers a unified approach.

• One schema, many accounting systems – Connect once, and you can support Fortnox, Visma, Björn Lundén, Tripletex, and more.
• Same endpoints everywhere – No need to learn multiple vendor-specific quirks.
• Faster to market – You can go live in weeks, not months or years.

With this model, adding Fortnox first is simple, and guess what.. swapping to another system later takes minutes, not months of rework. See a full tutorial of how to get your customer's Fortnox invoices here

Numbers That Matter

• 90% reduction in time to add a second ERP
• 98%+ invoice capture across systems
• Weeks, not months to go live

These aren’t abstract promises—they’re the kind of efficiency gains that can define whether your product scales smoothly or stalls under technical debt.

Build vs Buy in 2025

If your roadmap involves only Fortnox, and you have a dedicated integration team, building may still make sense. But if you need to connect to more than one accounting system, or simply want to stay focused on your core product, using a unified API platform is increasingly the rational choice.

The build vs buy debate isn’t new. But in 2025, with accounting systems multiplying and customers demanding flexibility, the trade-off is clearer than ever.

Get Started

👉 Create an account and start with Fortnox today, and swap to other systems in minutes.

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