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Winstwaker Developers

Developer hub for Dutch tax and accounting workflows

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What is Winstwaker Developers?

Winstwaker Developers offers a REST API that automates Dutch fiscal declarations, including VAT (omzetbelasting), dividend (dividendaangifte), income tax (inkomstenbelasting), and corporate tax (vennootschapsbelasting). Designed for technical entrepreneurs, it replaces complex legacy integrations with modern JSON endpoints, an OpenAPI specification, and official SDKs for Node.js and Python.

A sandbox environment lets you test without real data. Security is enterprise-grade with AES-256 encryption, IP whitelisting, and ISO27001 compliance. Authentication uses Bearer tokens with live and test prefixes.

Pricing starts at €49/month, which includes €49 credit. Credits are only consumed on successful definitive actions like submitted returns; sandbox requests, errors, and data retrieval are free. Volume discounts apply beyond the monthly credit. A developer portal tracks usage and manages API keys.

How to use Winstwaker Developers

  1. 1

    Sign up for a developer account via the Winstwaker Developer portal.

  2. 2

    Obtain API keys (ww_live_ for production, ww_test_ for sandbox) from the dashboard.

  3. 3

    Review the OpenAPI documentation and download the official Node.js or Python SDK.

  4. 4

    Test integrations in the sandbox without affecting real data or submitting to the tax authority.

  5. 5

    Send authenticated requests with proper payloads to endpoints to automate tax workflows.

Key features

Live VAT (Omzetbelasting) returns: submit quarterly or monthly sales data for automatic calculation.

Live dividend declarations: automate dividend filings for shareholders in bulk or on demand.

Income tax integration (beta): connect income and deductions to the inkomstenbelasting module.

Corporate tax filings (beta): generate VPB returns programmatically from annual accounts.

OpenAPI spec, SDKs (Node.js, Python), sandbox, and AES-256 encryption with IP whitelisting.

Use cases

  • SaaS founders automate periodic VAT returns by piping sales data from their invoicing system to the API.
  • ERP and backoffice systems leverage Winstwaker as an external fiscal engine for corporate or income tax.
  • Internal dashboards in Notion, Retool, or Looker Studio fetch real-time tax status for liquidity monitoring.
  • E-commerce sellers on Shopify, Bol.com, or Amazon integrate sales data for automated tax filing.

Best for

SaaS foundersERP developersTechnical entrepreneursFinance automation engineersDutch businessesIndie hackers with Dutch tax needs

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Frequently asked questions about Winstwaker Developers

Common questions to help you decide if Winstwaker Developers is right for you.

De standaard endpoints ondersteunen 100 requests per seconde per API Key. Zware asynchrone jobs hebben een eigen queue. Bij overschrijding krijg je een 429 Too Many Requests respons met Retry-After header.

Je betaalt een vast bedrag per maand, direct omgezet in tegoed. Alleen succesvolle, definitieve handelingen zoals een ingediende aangifte kosten credits. Sandbox requests, foutieve requests en data ophaalacties zijn gratis.

Authenticatie verloopt via Bearer Tokens met ww_live_ en ww_test_ prefixen. In het developer portaal kun je API keys revoken en whitelisten op IP-adres. Financiële data blijft in Nederland en wordt versleuteld opgeslagen.

Ja, API-gebruikers krijgen toegang tot een directe integratie-hulplijn. Je schakelt met engineers via een gedeeld Slack- of Teams-kanaal of via e-mail.

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