Fortnox API Integration
Fortnox is Sweden’s leading bookkeeping platform for SMBs and used by more than 600k SMB in the Nordics, offering integrated tools for accounting, invoicing, payroll and more.
Integrate now alongside dozens other Accounting platforms with Maesn.
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Have a Fortnox
Integration in Days
No Swedish ID showstopper
No Swedish credentials needed. Maesn gives you direct access to a Fortnox sandbox so you can start building today.
Fortnox Marketplace listing support
As an Fortnox technology partner, Maesn helps you meet all technical and security requirements to get your app reviewed and published in the Fortnox Marketplace.
Fortnox expert on your side
We have deep expertise in the Swedish market. We support you with country-specific, regulatory, and integration questions at every stage.
Clear docs, real sandboxes, fast integrations: How Hero Software builds with Maesn
Hero Software helps craft businesses digitize and automate their entire back-office — from quotes to invoicing. Over 40,000 tradespeople use their cloud-based platform to eliminate manual admin and run operations more efficiently.
“The support provided is truly first class, with impressively quick response times. The documentation is thorough and easy to follow, which made integration a smooth process for me. I also appreciate the wide range of accounting integrations and endpoints available. It's clear that the endpoints are continuously being developed and expanded, which adds even more value to the platform.”
Ricardas Kauneckas
Full Stack Engineer @ HERO Software
One API for Fortnox
and every system that comes after.
Unified. Certified. Production-ready.
Complete Fortnox data in a single request.
Fortnox list endpoints return only partial data by design. Multiple sequential API calls are required for full details. Maesn joins this into one, returning complete data in a single request.
No sequential calls for full data
Background joining, single complete response
Consistent with every other system in your stack
Extended Fortnox webhooks with Maesn.
Fortnox only supports webhooks for select objects like customers and invoices. Maesn combines native and synthetic webhooks to give you the same webhook experience across all Fortnox objects.
Native & synthetic webhooks combined
Every Fortnox object covered
Unified, normalized payloads
Pagination handled — consistent across all systems.
Fortnox paginates with a maximum of 500 records per page and requires manual page traversal. Maesn abstracts this entirely with unified limit and page parameters — consistent with every other system in your stack.
Max 500 records per page — handled automatically
Unified pagination parameters across all systems
No manual page traversal required
Get listed in the Fortnox marketplace with your own app.
Get your app officially reviewed and published in the Fortnox marketplace under your own name. Benefit from co-marketing activities and strengthen your positioning across Sweden.
Your app, your name — maximum growth effect
Get official Fortnox partner
Full integration support & co-marketing by maesn
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Everything you need to start today.
The Maesn docs cover every Fortnox endpoint, authentication flow, and implementation detail — plus a full overview of the current coverage, which is continuously being expanded.
Full Fortnox endpoint & authentication documentation
Current coverage overview at a glance
Continuously expanding endpoints & integrations
Get Fortnox partner and
listed in Fortnox marketplace with Maesn
Get your product and brand name listed in Fortnox marketplace,
reaching a large, concentrated base of swedish customers directly.
Whitepaper: European ERP & accounting market
Get insights and learn about the most imoportant systems in our country-by-country view of the European ERP and Accounting software landscape.
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3 Reasons why it is better to integrate Fortnox API with Maesn
Save months of effort
No need to build complexity workflows in Fortnox — Maesn removes months of learning and implementation effort.
Save thousands of euros
Avoid costly clarification rounds, external support and repeated coordination before going live.
Work with a proven partner
Maesn powers Fortnox integrations trusted by hundreds of companies — we know what works.
We are European.
Enterprise-grade security & compliance are our foundation.
Built and hosted in Germany to meet the highest security and compliance standards, Maesn processes API calls in real time without storing customer data and is fully ISO 27001 & GDPR compliant.
Read more in our related blog articles.
Everything you need to know about Fortnox
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Frequently asked
questions
You have more questions? We are looking forward hearing from you - book a meeting now!
What is Fortnox?
Fortnox is Sweden's leading bookkeeping and accounting platform for SMBs, used by more than 600,000 businesses across the Nordics, offering integrated tools for accounting, invoicing, payroll, and more.
Why should I integrate Fortnox via Maesn instead of directly?
Integrating via Maesn is faster, easier to maintain, and gives you immediate access to dozens of other ERP and accounting systems. Maesn handles OAuth, pagination, sandbox quirks, and compliance edge cases in the background.
Do I need a Swedish ID to get a Fortnox sandbox?
No. Maesn provides a Fortnox sandbox directly so you can start building immediately, without needing Swedish credentials or going through Fortnox's own registration process.
What data can I sync with Fortnox via Maesn?
Maesn supports a wide range of Fortnox data, including invoices, bills, credit notes, customers, suppliers, payments, transactions, journal entries, accounts, expenses, offers, and more.
How does Maesn handle Fortnox pagination?
Fortnox paginates with a maximum of 500 records per page and requires manual page traversal. Maesn abstracts this entirely with unified limit and page parameters, consistent across all supported systems.
Can I get listed in the Fortnox Marketplace through Maesn?
Yes. Maesn helps you meet all technical and security requirements to get your app reviewed and published in the Fortnox Marketplace.
How long does it take to integrate Fortnox with Maesn?
Most teams have a working Fortnox integration within days. Maesn provides sandbox access, thorough documentation, and direct partner support to get you to production fast.
How is my customers' data handled and stored?
Maesn uses HTTPS and TLS for all data transfer. Maesn does not store any customer data. The platform is hosted on Microsoft Azure in Frankfurt, Germany, and is fully GDPR compliant.
What happens if a Fortnox API request fails?
Maesn automatically returns a corresponding error code. You can monitor the status of all requests and resolve errors in real time via the Maesn portal, which provides full request and response logs.