Fortnox | Operate As Docs

Connect your client's Fortnox with a sign-in, and call its API through Operate As.

Website: fortnox.se
Connects by: Signing in with Fortnox
Category: Accounting
Services: 1
Tools: Pass-through only

Service	Key	Base URL
Fortnox	`fortnox`	`https://api.fortnox.se/3`

Connecting

Your client presses Connect on their link and approves on Fortnox's own screen. Operate As never sees their password.

Check they're connected

curl https://api.operate.as/v1/me/clients \
  -H "Authorization: Bearer $OPERATE_AS_API_KEY"

curl https://api.operate.as/v1/me/clients \  -H "Authorization: Bearer $OPERATE_AS_API_KEY"

Response

[
  {
    "id": "6f1c2a7e-...",
    "name": "Miller Dental",
    "services": [
      "fortnox"
    ]
  }
]

[  {    "id": "6f1c2a7e-...",    "name": "Miller Dental",    "services": [      "fortnox"    ]  }]

Permissions

What the client reads	Permission it asks for
See your company's details	`companyinformation`
See and change invoices	`invoice`
See and change customers	`customer`

Pass-through

Fortnox has no ready-made tools yet. Call any endpoint of its API through Operate As instead, with the client's access attached.

Add the client

In Clients, add your client and select Fortnox. Then send them their link.

Your client connects

They sign in with Fortnox and approve.

Find the endpoint

Pick the call from Fortnox's own API docs. Your path is everything after https://api.fortnox.se/3.

Send it through Operate As

Use the client's ID, the service key fortnox and that path. Your Operate As key goes in Authorization; the client's access is added for you.

See Pass-through requests for the full request and response format.

Call any endpoint

curl "https://api.operate.as/v1/clients/6f1c2a7e-.../fortnox/companyinformation" \
  -H "Authorization: Bearer $OPERATE_AS_API_KEY"

curl "https://api.operate.as/v1/clients/6f1c2a7e-.../fortnox/companyinformation" \  -H "Authorization: Bearer $OPERATE_AS_API_KEY"

Response

{
  "status": 200,
  "data": {
    "…": "the service's own response"
  },
  "encoding": "json"
}

{  "status": 200,  "data": {    "…": "the service's own response"  },  "encoding": "json"}

When access ends

Operate As renews the sign-in before it runs out and checks it daily. If Fortnox refuses to renew it, the service shows Expired, you're alerted, and your client reconnects from the same link.

See Keeping access alive and Removing access.

Calls answer

HTTP/1.1 409 Conflict
Content-Type: application/json

{
  "detail": "Miller Dental's Fortnox access ended. Send them their link to reconnect."
}

HTTP/1.1 409 ConflictContent-Type: application/json{  "detail": "Miller Dental's Fortnox access ended. Send them their link to reconnect."}

Your webhook receives

{
  "id": "evt_3f9a1c…",
  "type": "connection.expired",
  "createdAt": "2026-10-16T08:00:00+00:00",
  "data": {
    "clientId": "6f1c2a7e-...",
    "clientName": "Miller Dental",
    "provider": "fortnox",
    "services": [
      "fortnox"
    ],
    "reconnectUrl": "https://…"
  }
}

{  "id": "evt_3f9a1c…",  "type": "connection.expired",  "createdAt": "2026-10-16T08:00:00+00:00",  "data": {    "clientId": "6f1c2a7e-...",    "clientName": "Miller Dental",    "provider": "fortnox",    "services": [      "fortnox"    ],    "reconnectUrl": "https://…"  }}