Turn Exact Online into an API

What you can build on Exact Online

• Get outstanding items

  Build this

  Reads the Outstanding items overview under Sales for one administration: the open sales invoices for each customer account.

  Takes

  Administration, customer account (optional)

  Returns

  Account code, account name, invoice number, invoice date, due date, amount, amount in transit, currency, your ref, description

• List sales invoices by status

  Build this

  Reads the sales invoices of one administration from an invoice date you choose, with each invoice's status: Draft, Open or Processed.

  Takes

  Administration, status (optional), invoice date from

  Returns

  Invoice number, invoice date, customer, your ref, due date, amount, currency, status

• Create a draft sales invoice

  Build this

  Enters a new sales invoice for a customer with its lines and saves it as Draft, so someone can check it before it is processed.

  Takes

  Administration, customer, your ref, invoice lines (item, quantity, unit price)

  Returns

  Invoice number, customer, amount, currency, status

Automate Exact Online with a workflow

A workflow runs your methods as one process, with nobody at the screen. A schedule or a call from your own system starts it, the steps run in order, and the result arrives in your inbox or in the systems you already use.

• Overdue outstanding items, every administration

  Build this

  Starts

  Every weekday at 8:00

  Step 1

  For each administration you name, get the outstanding items.

  Step 2

  Keep the items whose due date has passed and that were not overdue on the last run.

  Step 3

  Email you the list grouped by administration and customer, with invoice number, invoice date, due date, amount and your ref.

• Processed sales invoices, posted to your system

  Build this

  Starts

  Every day at 18:00

  Step 1

  For each administration you name, list the sales invoices with status Processed and an invoice date from yesterday on.

  Step 2

  Keep the invoices that were not there on the last run, and stop when there are none.

  Step 3

  Post each one's invoice number, customer, your ref, invoice date, due date, amount and currency to your webhook.

You can run a workflow by hand on every plan, Free included. Schedules and webhook triggers come with the paid plans, from $29 a month.

Once built, one call from your code

Once you have built a method, it is one POST to /v1/runs from your backend, or a tool an AI agent calls over MCP. This is what “Get outstanding items” would look like.

curl https://api.fous.com/v1/runs \
  -H "Authorization: Bearer $FOUS_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{
    "method": "start.exactonline.nl/get_outstanding_items",
    "input": {
      "administration": "Acme Nederland B.V.",
      "customer_account": null
    }
  }'

{
  "status": "completed",
  "data": {
    "administration": "Acme Nederland B.V.",
    "items": [
      {
        "account_code": "20114",
        "account_name": "Northwind Trading B.V.",
        "invoice_number": 26000418,
        "invoice_date": "2026-10-14",
        "due_date": "2026-11-13",
        "amount": 4235,
        "amount_in_transit": 0,
        "currency": "EUR",
        "your_ref": "PO-7781",
        "description": "Order 2026-1187"
      }
    ],
    "count": 1
  }
}

An example with invented data, not a ready-made endpoint. The method exists in your organization once you build it, and its name, inputs and fields follow your request.

Exact Online’s own options

Exact documents a REST API for Exact Online that covers sales invoices, receivables, financial transactions, purchase entries and more, with webhooks. A customer can register an app for its own administration; connecting several customers takes the Exact Online Developer subscription at €15 a month. Calls are limited to 60 a minute per administration, with daily limits per app and per administration.

Read on November 12, 2026: Exact Online Developer subscription, Exact Online REST API resources, Exact Online Volume Packs and API limits.

Signing in to Exact Online

Exact Online asks for your user name and password, then the verification code from an authenticator app. You can trust a browser for 30 days, after which the code is asked again. With Fous you sign in through Exact Online's own sign-in with your own account: the login is sealed with AES-256 and never shown to code or AI agents.

Worth knowing

Limits count per administration

The API allows 60 calls a minute per administration. Outside Premium each app gets at most 5,000 calls a day, and an administration at most 20,000 a day in all. Each XML call counts as 50.

Processed invoices are final

Draft invoices stay out of financial reports and balances. Open invoices can still be changed. Processing happens through printing, and a processed invoice cannot be changed or reopened.

Each country is its own Exact Online

Exact Online runs on a separate website per country, so the address depends on the country: start.exactonline.nl for the Netherlands. The Developer subscription has its own sign-up for each country.

A partial payment keeps the item open

When a customer pays part of an invoice, the outstanding amount stays on the Outstanding items list. Amount in transit shows what you have asked your bank to pay.

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