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Winstwaker Developers
Developer hub for Dutch tax and accounting workflows
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
Sign up for a developer account via the Winstwaker Developer portal.
- 2
Obtain API keys (ww_live_ for production, ww_test_ for sandbox) from the dashboard.
- 3
Review the OpenAPI documentation and download the official Node.js or Python SDK.
- 4
Test integrations in the sandbox without affecting real data or submitting to the tax authority.
- 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.
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Frequently asked questions about Winstwaker Developers
Common questions to help you decide if Winstwaker Developers is right for you.