The Finnish Tax Administration published its quarterly News for Software Developers – 04/2026 on 23 September 2026, detailing technical specifications and API changes for the MyTax ecosystem. The release covers updates to the Incomes Register (Tulorekisteri) interface, e-invoicing validation rules, and the new Suomi.fi Messages integration layer. Developers of payroll, ERP, and tax compliance software must implement these changes by the mandatory cutover date of 1 January 2027 to maintain certified connectivity.
Key Takeaways
- Incomes Register API v3.2: Introduces mandatory field-level encryption for sensitive income types (e.g., fringe benefits, stock options) and deprecates the legacy CSV upload endpoint effective 30 June 2027.
- E-Invoicing Validation Enhancements: New Schematron rules enforce stricter VAT ID cross-checks and require the Buyer Reference (Viitenumero) on all B2G invoices. Non-compliant invoices will be rejected at the platform gateway.
- Suomi.fi Messages Integration: A new RESTful endpoint allows software to push secure notifications to taxpayers’ Suomi.fi inboxes, replacing email for official decisions. Implementation requires OAuth2 client credentials granted via the Tax Administration’s certificate service.
Disclaimer: This article is compiled and summarized by the AI based on publicly available information and is for general information purposes only. It does not constitute any form of formal tax advice, legal opinion, or basis for performance. Please consult a qualified professional tax advisor or legal counsel for tax advice.
Source: Read Official Announcement