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After a two-month public consultation period, Hungary’s National Tax and Customs Administration (NAV) has finalized changes to the Online Invoice System’s business validation logic, incorporating feedback from taxpayers and technical stakeholders. The revised rules will take effect in the live production environment from September 15, 2025, with the test environment available from September 1, 2025.
These updates aim to improve data accuracy and quality across Hungary’s real-time invoice reporting system, which serves both the tax authority and businesses leveraging NAV services such as Online Számla and eVAT (eÁFA).
Key Changes to Business Validations
NAV has introduced the following adjustments to the Online Invoice System’s validation rules:
- 3 new WARN messages (non-blocking warnings) will be added
- 3 existing WARN messages will become inactive
- 1 INFO message will be elevated to a WARN
- 15 WARN messages will be reclassified as ERROR messages (down from the originally planned 21)
This means:
- ERROR messages indicate critical technical or content issues that block data submission.
- WARN messages do not block submission, but signal potential business logic issues that may result in inaccurate or non-compliant invoice data. Businesses are strongly encouraged to review and correct these warnings.
Why It Matters
Accurate invoice data is vital not only for tax compliance but also for the integrity of connected systems, including machine-to-machine (M2M) integrations and web-based query services increasingly used in both the issuer’s and recipient’s side of invoicing.
To avoid rejected submissions, ensure proper VAT reporting, and maintain smooth eVAT operations, NAV recommends periodic reviews of validation messages and prompt action to correct any flagged issues.
Action Steps for Businesses and Developers
- Review the updated validation rules published on NAV’s official GitHub page
- Coordinate with software developers to ensure invoicing systems are updated by September 15
- Use the test environment starting September 1 to simulate and verify compliance before going live
- Pay attention to reclassified ERROR messages, as failure to comply will block invoice data transmission to NAV
Final Notes
NAV highlights that the shared goal of high-quality, machine-readable invoice data supports both regulatory enforcement and business efficiency. Businesses that rely on real-time tax reporting and automated VAT systems must ensure their software is ready for the updated validation logic.
For ongoing updates and developer discussions, visit the NAV GitHub discussions page.
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