The A1 certificate: which country do you pay social security in?

What the A1 certificate actually does

The A1 is a portable document issued by a national social security institution. It states, in a form recognised across the EU, EEA and Switzerland, that the holder is subject to the social security legislation of a named country for a defined period.

Its purpose is to prevent two outcomes that the coordination rules treat as equally unacceptable: double contributions (paying in two countries for the same work) and no contributions at all (falling between two systems). The regulation resolves this by assigning each worker to exactly one system, and the A1 is the evidence of that assignment.

An important clarification: the A1 concerns social security, not income tax. Where you pay tax on your salary is determined by domestic law and by double taxation treaties, and the answer can differ from where you pay contributions. It is entirely possible to pay income tax in one country and social security in another. Treating the A1 as a tax document is a common and costly error.

The default rule and its exceptions

The default rule is simple: you are subject to the legislation of the country where you physically work. If you live in Slovakia and work in Hungary, Hungarian social security applies. No A1 is needed for this — the situation is unambiguous.

The A1 exists for the exceptions, of which three matter most.

Posting. An employer established in one member state sends an employee to work temporarily in another. If the posting is expected to last no more than 24 months and the worker is not replacing another posted worker, the home country's legislation continues to apply. A Hungarian company sending an engineer to Austria for eighteen months keeps that engineer in the Hungarian system — with an A1 issued by NAV.

Multi-state work. Someone who habitually works in two or more member states. Here the rules are more intricate. If you carry out a substantial part of your activity in your country of residence — as a rule of thumb, at least 25% of working time or remuneration — that country's legislation applies. If not, the location of the employer's registered office generally decides.

Self-employment. A self-employed person who normally pursues activity in one member state and temporarily moves it to another may remain in the home system, again subject to the 24-month limit and to the requirement that the activity be similar.

Remote work has made this harder

The regulation was written for factories and construction sites, not for laptops. The rise of cross-border remote work has made the multi-state rules considerably more relevant — and more contested.

Consider a Hungarian resident employed by an Austrian company who works three days a week from home in Budapest and two days in Vienna. That is 60% of working time in the country of residence, comfortably above the 25% threshold. Hungarian legislation applies, and contributions are due in Hungary — even though the employer is Austrian and might expect otherwise. The employer must register in Hungary for this purpose.

Reverse the ratio — one day at home, four in Vienna — and the outcome flips. Twenty per cent falls short of the substantial-part threshold, so the employer's seat decides, and Austrian legislation applies. Same two countries, same people, different answer, driven entirely by a percentage.

Because the threshold is assessed prospectively over the following twelve months, and because working patterns drift, this is an area where a change in habits can quietly change your legal position. Reviewing the arrangement annually is prudent rather than paranoid.

How to obtain an A1 in Hungary

In Hungary the A1 certificate is issued by the National Tax and Customs Administration (NAV). The application is filed electronically, using the designated form, and is submitted either by the employer (for posted employees) or by the individual (for the self-employed).

The application asks for the details that determine the outcome: the identity of the employer and worker, the countries involved, the expected duration, the nature of the activity, and — for multi-state cases — the distribution of working time between countries. Supporting documents may be requested.

Two practical points. First, filing requires Hungarian electronic identification, which for foreign nationals means Ügyfélkapu+, since the DÁP profile is not available to them. Second, apply before the work abroad begins. Retrospective issuance is possible but is not something to rely on, and in the interval you are exposed.

What happens without one

Labour inspectorates across the EU check for A1 certificates, and in some countries the checks are routine on construction sites, in road transport and in the hospitality sector. A worker who cannot produce an A1 is presumed to be subject to the legislation of the country where they are working.

The consequences follow from that presumption. The host country may demand contributions for the entire period of the posting, with interest. Administrative fines are common, and in several member states they are substantial. The employer typically bears the cost, but the disruption — a site shut down pending documentation — is shared.

There is also a quieter risk. Contributions paid into the wrong system do not simply transfer. Recovering them requires an administrative procedure between two institutions, and while it is under way the worker's pension record and entitlement to benefits may be uncertain. The A1 is cheap; the alternative is not.

What the A1 does not cover

Three limits are worth stating plainly.

It is not a work permit. Third-country nationals still need the appropriate immigration authorisation. The A1 says nothing about the right to work.

It does not apply outside the coordination area. The EU, EEA and Switzerland are covered. For other countries, bilateral social security agreements may apply — Hungary has several — but the A1 form itself is not the instrument. A digital nomad working from Budapest for a US employer under the White Card is outside this framework entirely.

It does not settle your income tax. Worth repeating, because it is the single most common misunderstanding. If you are unsure where your salary is taxable, the relevant instrument is the double taxation treaty, and our expat tax guide is the better starting point.

Frequently asked questions