E-invoice registration: Who is required to register, and what are the deadlines?

There is a lot of confusion surrounding the term “e-invoice registration” because, in practice, it is often used to refer to several different obligations. Sometimes this refers to notifying the National Tax and Customs Administration (NAV) of the use of invoicing software; other times, it refers to setting up data reporting for NAV Online Invoicing; and in other cases, it involves arranging for the customer to accept electronic invoices.

In this article, we’ll break these down and clearly explain who is required to comply, what the deadlines are, and what you should keep in mind to avoid compliance issues with e-invoicing.

What exactly does “e-invoice registration” mean in Hungary?

Most business leaders and finance professionals confuse three issues:

1) Registration of invoicing software with the National Tax and Customs Administration (NAV)

If you issue invoices using invoicing software (desktop software, an ERP module, or cloud-based invoicing software), you are generally required to report its use to the National Tax and Customs Administration (NAV) using the appropriate form. This is not the same as submitting invoice data.

2) NAV Online Invoice Data Reporting (registration, technical user, integration)

In the NAV Online Invoice system, the provision of invoice data is currently the most widely required obligation. The exact scope of this requirement may vary depending on the invoice type, tax status, and method of issuance; therefore, it is always advisable to check the NAV’s current guidelines. Starting point:

• NAV Online Invoice

3) The buyer’s (partner’s) acceptance of electronic invoices

A typical condition for the validity of an “e-invoice” (i.e., an electronic invoice) is that the buyer accepts the electronic invoice (for example, in a contract, in the General Terms and Conditions, or through a verifiable process). This is not a notification to the National Tax and Customs Administration (NAV), but rather a mutual agreement between the parties.

Useful background material on the conceptual foundations (legal and technical requirements: authenticity, integrity, legibility): How to implement electronic invoicing?

Who is required to register for e-billing?

The best answer: it depends on which "notification" we're talking about. The table below will help you quickly figure it out.

To access ONYA and fill out forms, start by visiting the NAV website: NAV ONYA.

What are the expected deadlines? (detailed breakdown)

Reporting invoicing software: the most common obligation, yet the one most easily overlooked

In practice, one of the most common “administrative oversights” is when a company implements a new invoicing system (or ERP invoicing module) but fails to register the software with the National Tax and Customs Administration (NAV).

The company routine that usually works:

• When a new billing system is implemented, the finance and IT departments jointly document the software details (name, version, provider, operation).

• The designated person initiates the notification in ONYA.

• When making changes (such as upgrading to a new version, adding a new module, or switching providers), you update it in the same way.

The deadline is typically 30 days from the start of use (and the same applies after any changes or discontinuation). Since the specific rules may vary depending on exactly which solution you use and how you use it, it is advisable to consult with an accountant or tax advisor.

Online Billing: Registration and Technical User—Not on the Morning of the Launch Day

If the invoicing software/ERP system submits the data electronically, the following are typically required:

• Online Invoice Access (Admin Permissions)

• technical users and keys

• for testing (especially in the case of ERP integration)

Here, the “deadline” is not just a legal requirement but an operational reality: if access and the technical user are not in place on time, data reporting could fail on the first live billing day.

A separate document on minimum requirements for access and permission management (MFA, roles, auditability): E-invoice login: access management and security minimums

Online Invoice Data Reporting: Real-Time Principle, Exceptions, and Error Handling

From a corporate compliance perspective, it’s not just about being “on board,” but also about:

• In case of an error, there is a retry/backoff mechanism and idempotence

• There is a log (what went through, what didn't)

• is responsible for monitoring and repairs

If you're having trouble with this, here's a quick, practical guide: NAV e-invoicing: common mistakes and quick fixes for businesses

Customer Acceptance: When Is It Required, and What Should Be Documented?

If you send e-invoices to your business partners (for example, as a PDF via email or in a structured format), it is good practice to document the rules for acceptance and delivery in order to prevent disputes.

The minimum that should be specified (in a contract or in the General Terms and Conditions):

• The customer accepts the electronic invoice

• Delivery channel (email address, portal, EDI, PEPPOL, if applicable)

• When do you consider a message to have been delivered (e.g., sent + no error-free bounce-back)

• What is the procedure if the customer hasn't received the item or is disputing it?

This is not a standard “deadline notification,” but rather a prerequisite: it must be completed no later than before the first e-invoice is sent.

Quick checklist: Find out in 15 minutes if you're good to go

The following short list will help ensure that the “report” is not just on paper, but is also auditable.

• We have designated a person in charge of registering the invoicing software (Finance), and we have the IT contact.

• Do you know what billing components are available (specifically: billing module, ERP module, manual invoicing, and online store)?

• Access to the online billing admin panel is not limited to a single person, and multi-factor authentication (MFA) is in place.

• The integration test suite includes test data that can be replayed.

• There are logs and reports indicating which invoices have been successfully reported.

• When handling errors, you know what to include (request ID, XML, response code, timestamp).

Common mistakes that mean you “have an e-invoice” but still aren’t in compliance

The registration is complete, but the permissions cannot be audited

It’s common for everyone to be an “admin” or for technical user credentials to be shared across multiple systems. This isn’t just a security risk; it also looks bad during an audit.

The connection is working, but there is no monitoring

Data reporting typically breaks down when:

• An API or XSD changes on the provider side

• A version update is taking place in the billing system

• Due to a data quality error, incorrect invoices are piling up

Without monitoring, this could remain hidden for days.

Disputes will arise due to a lack of mutual understanding

Technically, you can send the e-invoice, but the customer disputes whether they accepted it or when they received it. A short clause in the contract is much cheaper than a lengthy dispute.

When is it worth bringing in outside help?

Many companies can answer the question “Is it mandatory, and what is the deadline?” with the help of an accountant. External IT or integration support comes into play when compliance becomes a system-wide issue:

• You issue invoices from an ERP system (or multiple systems) and need to coordinate multiple invoice sources

• There are a large number of accounts, and we need reliable retry, monitoring, and reporting capabilities

• There are multiple locations, multiple companies (a group of companies), and separate access rights

• The goal is no longer just compliance with the National Tax and Customs Administration (NAV), but automation "from e-invoicing to accounting"

At this stage, the typical task is not a single notification, but rather a brief audit and a stabilization package: processes, permissions, integration, logging, and error handling.

Frequently asked questions (FAQ)

Is “e-invoice registration” the same as the Online Invoice data reporting system? No. Although the terms are often used interchangeably in everyday language, registering the invoicing software, connecting to the Online Invoice system, and the recipient’s acceptance of e-invoices are three separate matters.

If I use a cloud-based invoicing service, do I still need to register an invoicing program? In many cases, yes, because the tax authority (NAV) doesn’t care whether it’s cloud-based or not; what matters is that you issue the invoice using an invoicing program. It’s best to consult your accountant about the specific steps to take.

What is the deadline for registering an invoicing program? In practice, the deadline is typically 30 days after the start of use (or any changes or discontinuation). Since the specific rules may vary depending on the circumstances, please review the NAV’s guidelines and consult with an expert.

Is separate consent from the customer required for e-invoicing? In many business situations, it is strongly recommended, and to avoid disputes, it is best practice to set this out in writing (contract/terms and conditions). The exact form and requirements may depend on the type of e-invoice and the agreement between the parties.

What should I do if there is an error in the Online Invoice data reporting? First, perform a triage: data, format (XML/XSD), integration, or operations. A good starting point for practical troubleshooting steps: NAV e-invoice: common errors and quick solutions for businesses.

Next step: Turn the "reporting" into a stable, auditable process

If your e-invoice implementation involves multiple systems (ERP, online store, multiple locations, third-party providers), or if you’ve had issues with data reporting to the National Tax and Customs Administration (NAV) in the past, it’s a good idea to start with a brief, targeted assessment.

The Syneo team can assist with IT and digitalization aspects of streamlining invoicing processes, stabilizing the NAV Online Invoice integration, managing user permissions, monitoring, and related automation.

Contact us: syneo.hu