Pull your Twinfield receivables into your own systems

What you can build on Twinfield

• Get open items per debtor

  Build this

  Reads the Openstaande postenlijst per debiteur (open items per debtor) under Rapporten > Rapporten > Debiteuren for one administratie.

  Takes

  Administratie, debtor (optional), up to period (optional)

  Returns

  Debtor code, debtor name, invoice number, invoice date, due date, currency, invoice amount, open amount

• Get the aging analysis per debtor

  Build this

  Runs the Ouderdomsanalyse per debiteur (aging analysis), which splits each debtor's open items into up to 30, 31 to 60, 61 to 90 and over 90 days.

  Takes

  Administratie

  Returns

  Debtor code, debtor name, up to 30 days, 31 to 60 days, 61 to 90 days, over 90 days, total open

• Get a debtor's account card

  Build this

  Reads the Debiteurenkaart (debtor card) for one debtor: every entry posted to that debtor in the period you choose.

  Takes

  Administratie, debtor, from period, to period

  Returns

  Date, journal, entry number, invoice number, description, debit, credit, balance

• Assign a bank line to an invoice

  Build this

  In the Bankenmodule, opens Toewijzen bankregels (assign bank lines), matches one bank line to an open sales invoice and leaves the statement unposted for review.

  Takes

  Administratie, bank account, bank line date, amount, invoice number

  Returns

  Bank line, invoice number, debtor, assigned amount, unassigned amount

Automate Twinfield 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.

• Debtors over 90 days, every administratie

  Build this

  Starts

  Every Monday at 7:00

  Step 1

  For each administratie you name, get the Ouderdomsanalyse per debiteur.

  Step 2

  Keep the debtors with an amount in the over 90 days column.

  Step 3

  Email you the list, one section per administratie, with the total open per debtor.

• New open items, posted to your collections system

  Build this

  Starts

  Every weekday at 8:00

  Step 1

  For each administratie, get the open items per debtor.

  Step 2

  Keep the items that were not there on the last run.

  Step 3

  Post each one, with debtor, invoice number, due date and open amount, to your webhook.

• Month-end receivables summary for your team

  Build this

  Starts

  Monthly on the 3rd at 9:00

  Step 1

  For each administratie, get the open items per debtor up to the period that just closed.

  Step 2

  Have an AI step summarize the total open and the five largest debtors per administratie.

  Step 3

  Email you the summary.

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 open items per debtor” would look like.

curl https://api.fous.com/v1/runs \
  -H "Authorization: Bearer $FOUS_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{
    "method": "login.twinfield.com/get_open_items_per_debtor",
    "input": {
      "administratie": "Acme Holding B.V.",
      "debtor": "1003"
    }
  }'

{
  "status": "completed",
  "data": {
    "administratie": "Acme Holding B.V.",
    "report": "Openstaande postenlijst per debiteur",
    "items": [
      {
        "debtor_code": "1003",
        "debtor_name": "Northwind Trading B.V.",
        "invoice_number": "20260418",
        "invoice_date": "2026-09-30",
        "due_date": "2026-10-30",
        "currency": "EUR",
        "invoice_amount": 4235,
        "open_amount": 4235
      }
    ],
    "total_open": 4747.5,
    "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.

Twinfield’s own options

Wolters Kluwer documents the Twinfield API, made of webservices and REST APIs, for importing sales, purchase, cash and journal transactions and for retrieving customers, suppliers, transactions and open invoices. A client ID that is not yet certified gets 5% of the normal rate limits, and Wolters Kluwer does not support higher limits.

Read on November 12, 2026: Twinfield API: Fair Use Policy and Limitations, API Best Practices: Introduction, Welke functies zijn er per Twinfield abonnement beschikbaar?.

Signing in to Twinfield

You sign in to Twinfield at login.twinfield.com with your own Twinfield user, and your role, from LVL1 to LVL9, decides which modules and reports you see. With Fous you sign in once through Twinfield's own sign-in with that account: the login is sealed with AES-256, never returned by the API or written to logs, and code and AI agents never see it.

Worth knowing

Your role decides which reports you get

The role of a user sets the reports and modules it reaches. An LVL4 user can request the Openstaande postenlijst debiteuren, while an LVL5 user only enters journals and requests the Invoerverslag.

One administratie at a time

An accountant's environment holds many administraties, and the API identifies each one by its office code. Reports run inside one administratie, so a method takes the administratie as an input.

Two bank modules side by side

The Classic bankenmodule, the orange tiles Bankafschriften and Boekingsinstructies, stays available: its phase-out planned for 31 October 2026 is postponed until further notice. Say which module a method should use.

Service Desk entries wait for approval

A Basis Boekhouden (SD) user can save transactions only as potloodboekingen (pencil entries), which are offered to the superuser for authorization before they count.

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