NAV M2M and the ÁNYK phase-out: professional preparation for 2027

By Kovács András

ÁNYK is phased out on January 1, 2027. A practical guide for accountants on the NAV M2M transition — deadlines, registration, and key decisions.

What exactly is being discontinued, and what isn't?

NAV's official communication of December 5, 2025 confirmed what the industry had suspected for some time: the General Form-Filling Framework Program (ÁNYK) cannot be used to submit new returns from January 1, 2027. ÁNYK will not disappear immediately after that — it will continue to function temporarily for self-revision of previously submitted returns — but daily work must flow through a new channel.

According to NAV, more than 30 million forms are submitted to ÁNYK annually. This traffic will migrate to two channels: ONYA (manual, browser-based completion, for lower volumes), and the NAV M2M general machine interface (automated, software-initiated submission, primarily for accountants, tax advisors, finance and accounting professionals, and larger taxpayers).

Anyone currently using ÁNYK in practice faces two decisions: which channel they will work on, and with what software. The question is professional in nature, not merely technical.

What does M2M mean in accounting practice?

M2M (machine-to-machine) simply means that a registered software communicates directly with NAV's system. From an accountant's perspective, this has three important implications.

First: there is no separate "M2M login." After a single registration, the software manages — based on existing power of attorney authorizations — on whose behalf it can perform data communication.

Second: batch submission of returns is a native part of the process. What worked as batch submission in ÁNYK is even more automatable in M2M — scheduled, combined with approval logic, initiated from business management software.

Third: submission and status tracking are guaranteed. The receipt and error notification arrive in the storage space and, in properly designed software, can be linked back to the original return.

It is important to clarify a misconception: NAV does not provide a "downloadable M2M client." M2M is intentionally a developer tool; software companies build products on top of it that they make available to end users (accountants, accounting firms, businesses).

Where does M2M stand now? (And what does this mean in practice?)

The system has been live since early October 2024. According to published data, tens of thousands of electronic forms were submitted via the M2M channel in the first year — still far from ÁNYK's 30 million volume, but the growth trajectory is clear.

Two important milestones occurred recently: in February 2025, legislative amendments made it possible for organizations — not just natural persons — to complete end-user registration; and on October 6, 2025, the data query service launched in the live environment.

As an initial query package, the following can be queried: tax account data, employment notifications, list of missing returns, and public debts transferred for enforcement. Based on market feedback, the query channel is stable and provides daily operational value to those who integrate it into their workflows.

What's coming in 2026? NAV's roadmap

Based on milestones published on the NAV GitHub wiki, 2026 will be the year of the new Document API. This does not replace the existing API but goes live alongside it, built on more transparent, modern document formats instead of the old ÁNYK structure.

According to NAV, these are planned dates and may change — but the direction is stable.

The new API brings two significant professional innovations. One is that NAV will publish return-completion rules — instead of the previous PDF completion guides — in a format that accounting software can directly read and automatically apply; a rule change therefore no longer needs to be manually tracked with every software update. The other innovation is a real-time validation service, with which the software can query NAV before submission to check whether a given return is in order. Both serve the same goal: errors should appear on the accountant's own screen, not after NAV-side processing in an already-submitted return.

7 months, four decisions — what does an accounting firm need to handle now?

The transition is not an IT project, but four interconnected professional decisions.

1. Representation and registration structure

Questions to clarify: who registers within the accounting firm on the ÜPO (Client Portal)? How does M2M registration connect to existing standing authorizations? Who manages the API keys?

These are not hypothetical questions. According to NAV regulations, M2M operations are ultimately tied to a specific registered natural person — so in an accounting firm, it is not only the software that needs to be set up, but the chain of responsibility must also be defined.

2. Software selection (or coordination with your vendor)

The practical question is simple: does the payroll software, accounting software, or tax software currently in use already support M2M, and if so, at what pace will it also support the new Document API? If the current vendor does not yet support it, what is the development timeline? If it does, what features are supported (submission only, or also data querying)?

These are questions that need to be asked in the first half of 2026, so there is time to test by year-end and switch if necessary.

3. Client communication

Most clients will not know what M2M is, and they don't need to. What they need to know: how the accounting firm will submit returns on their behalf from 2027, and what changes for them. The typical question will be: "Do I need to do anything?"

In most cases, the answer is: the accounting firm handles it, but it is worth informing clients.

4. Internal processes and risk management

An accounting firm is by nature a risk concentration point. If something goes wrong, it causes problems for many clients' returns simultaneously. NAV M2M requirements (encryption, logging, audit trail) are not optional considerations — the chosen software must mandatorily fulfill these.

NAV's client program requirements — including secure storage of identification keys, auditability of user operations, and deletion of keys upon termination of access — are obligations that apply to the software.

Typical mistakes that can be avoided now

Procrastinating until the second half of 2026 — it is worth consulting with experts and beginning preparation now.

Confusing NAV M2M with eÁFA M2M — these are two separate channels with separate rule systems.

The misconception of building your own client program — most accounting firms should not develop their own client.

Mixing test and live environments — the test API key is not valid in the live environment.

Skipping data querying — which can already save daily minutes in practice today.

What should you concretely do now?

The remaining time is short from a professional standpoint. A reasonable schedule includes the following steps:

Before summer 2026: clarify representation and registration structure, complete M2M registration, hold first consultation with software vendor.

Summer–autumn 2026: finalize software selection, testing (preferably in the new Document API test environment), integrate available M2M features into daily work.

Autumn–winter 2026: finalize internal processes, client communication, submit the last ÁNYK returns, run parallel operations.

From January 2027: exclusively M2M and ONYA.

NAV M2M is itself a well-documented, live technology. The question is not whether the transition is possible — it is, and an ever-growing share of the market is already using it, but many changes will still appear in the near future, so it is worth starting preparation and familiarization with the system now.

Frequently asked questions

How long can ÁNYK still be used?

ÁNYK can be used to submit new returns until December 31, 2026. From January 1, 2027, it can only be used for self-revision of previously submitted returns, not for new submissions. After that, all new submissions go through NAV M2M or ONYA.

Is the use of NAV M2M mandatory?

No, it is an alternative channel. NAV recommends M2M primarily for accountants, tax advisors, and larger taxpayers who submit many returns or want software integration. Those who handle returns manually in small volumes can continue using ONYA after 2027.

What is the difference between NAV M2M and eÁFA M2M?

These are two separate channels. The general NAV M2M is built for a wide range of documents (typically replacing ÁNYK forms), while eÁFA M2M is a separately designed system specifically for VAT return submission, with its own XSD and business process. The two do not replace each other, but coexist in parallel.

Is separate registration required for each client business?

No. An accounting firm needs only a single M2M registration; NAV manages — based on existing power of attorney authorizations — on whose behalf the software can act. This is one of the greatest practical advantages over browser-based ÜPO solutions.

Can a company or accounting firm register for M2M, or only a natural person?

Both, since February 1, 2025. With the introduction of M2M 2.0, organizational registration is also possible, so accounting firms, accounting organizations, and any business entity can register as a user in their own name.

Do we need to develop our own software for M2M?

The vast majority of accounting firms do not. NAV intentionally designed M2M so that software companies build products on top of it; the relevant question for a practice is whether the business management or return software currently in use already supports M2M. Developing your own client program is only justified for special internal integration needs.

What can be queried via M2M?

Available in the live environment from October 6, 2025: tax account data (aggregate and itemized), employment-related notifications, list of missing returns, and public debts transferred for enforcement. NAV has indicated that the package will expand.

What happens if we don't transition by January 1, 2027?

After that, new returns cannot be submitted in ÁNYK. Those who have not transitioned can submit returns manually via ONYA — which is not sustainable for many clients, so an unprepared 2026 represents a serious operational risk for accounting practices.

How much does the M2M transition cost?

NAV registration and the M2M channel itself are free. The cost arises in the licensing of the chosen software and any internal process development.

Where can official NAV resources be found?

NAV publicly publishes the complete technical documentation, milestones, FAQ, and schema descriptors for M2M at github.com/nav-gov-hu/M2M. The wiki, SwaggerHub API descriptor, and the developer Discussions forum are also available there.