As of September 15, 2025, the Hungarian Tax Authority (NAV) will further tighten the rules governing online invoice data reporting. These changes reflect NAV’s strengthened commitment to improving data quality and accuracy.

Businesses should proactively prepare by reviewing their XML-based data submissions, as reporting errors may result in penalties of up to HUF 1 million per invoice.

What’s changing in the NAV online invoice reporting process?

According to NAV’s official statement, from September 15, 2025, a total of 15 messages previously categorized as WARN (warnings) will be reclassified as ERROR messages. This means that any data submission triggering these messages will be automatically rejected by the system.

Additionally, 3 new WARN messages will be introduced, reflecting NAV’s continuous efforts to improve reporting accuracy.

These changes are closely tied to the broader objectives of the eVAT (eÁFA) system, which relies on high-quality invoice data. Errors or omissions not only hinder NAV’s oversight but also increase compliance risks for taxpayers.

When do the new rules take effect?

  • From September 1, 2025: The new validations will be available in the NAV test environment.
  • From September 15, 2025: The validations become mandatory in the live production environment.

From this point onward, submissions that previously triggered only WARN messages will now be rejected with ERROR messages.

What is the difference between WARN and ERROR messages?

  • WARN (Warning): The data submission is accepted, but a warning message is returned, indicating a potential issue with the content. These should not be ignored, as they often signal inconsistencies or problems with system configuration.
  • ERROR: The data submission is rejected, and the system does not process it further. This is treated as non-compliance, which may lead to significant financial penalties.

The stricter validation rules coming into effect in September may require modifications to XML data reporting and system configurations. RSM’s tax IT expert team offers an automated solution to review invoice data submitted over the past two years and identify whether your company is affected by newly categorized ERROR messages — all without the need to provide invoice lists or reports. If needed, we provide recommendations for adjusting technical settings and the XML generation logic to help you avoid data reporting rejections and potential fines of up to HUF 1 million per invoice.

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Penalties for faulty reporting: Up to HUF 1 million fine per invoice

Since August 1, 2024, NAV has adopted a stricter stance on incomplete or incorrect online invoice reporting. Under current regulations, each invalid or rejected submission can result in a fine of up to HUF 1,000,000.

This risk is particularly high when an ERROR message causes automatic rejection, and the issue goes unnoticed by the taxpayer.

What validations are affected?

The 15 affected messages were previously only warnings but will now block submission. From the earlier draft list of 21 messages:

  • Several will remain as warnings.
  • Three will be removed entirely.

Consider a practical example:

When reporting an intra-community supply of goods (KBAET), the buyer type must be set to OTHER. This reflects the VAT-exempt nature of such transactions.

If the buyer is mistakenly marked as DOMESTIC, this previously triggered only a WARN message, and the submission was accepted. Starting in September, however, this will now result in an ERROR, and the data will be rejected.

Other notable examples from the updated ERROR list include:

  • Mismatch between currency (e.g., HUF) and the provided exchange rate.
  • A correction invoice having the same serial number as the original invoice.
  • Performance period end date being earlier than the start date.
  • Domestic reverse charge marked, but the buyer is not a domestic VAT entity.

WARN messages may signal system issues – best addressed proactively

While WARN-type messages do not block data submission, they should be taken seriously. As confirmed by NAV and supported by our own experience, many organizations do not treat these warnings with the seriousness they deserve—despite the fact that they often signal significant data quality problems or systemic anomalies.

Even aside from the 15 new ERROR-type validations, audits of the Online Invoice system frequently reveal missing mandatory data or submissions with incorrect content. In the absence of proper internal controls, such issues typically only come to light during tax audits or data reconciliation procedures.

It is important to note that the Online Invoice system does not verify the factual accuracy of the reported invoice data. For example, the reported performance date might not match the actual date on the invoice. In such cases, the system does not generate a warning or error message. The data is accepted as valid, and the user may incorrectly assume that everything is in order—only to discover the mistake later.

In one of our recent case studies, we described how such an issue was uncovered during a NAV audit, and how a prompt correction helped minimize potential risk.

As mentioned earlier, from August 1, 2024, NAV may impose fines of up to HUF 1 million per invoice for missing or incorrect data reporting. For this reason, we strongly recommend regular internal audits and proactive data quality checks for all invoice data submissions.

Is your system ready for the upcoming changes?


The introduction of these new validations presents significant technical and compliance challenges for companies.

If you are not confident that your systems are generating fully compliant XML-based invoice submissions, or if regular review of WARN messages is not currently part of your internal processes, it’s advisable to act now to ensure your system is fully prepared.

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Data quality in the spotlight

Stricter validation rules are not only in NAV’s interest—they also support the daily work of businesses and accountants who rely on the Online Invoice system.

Clean, consistent data enables:

  • More reliable invoice processing automation
  • Stronger control over VAT analytics
  • Lower risk of compliance issues and penalties

NAV is becoming increasingly consistent in enforcing data quality expectations—and for good reason: the eVAT (eÁFA) system can only function effectively if the invoice data is accurate, complete, and reflects real transactions.

The bottom line: technical compliance is just the starting point—your data must reflect real transactions, and your reporting must be both complete and accurate.

NAV Online Invoice Issues and Data Quality Check