The document that decides more than the policy does
An employer moving someone from Rotterdam to Zurich, or from Munich to Shanghai, generally starts with the insurance. Which plan, which area of cover, which limits, whether the family is included. That is the visible part of the decision and it is the part the broker is paid to answer.
It is rarely the part that determines whether the employee must enrol in the host country's health system. That is decided by social security law, on the basis of a certificate issued by the home country's institution, and it is decided independently of how good the private cover is. A posting supported by the right certificate can escape a compulsory local scheme entirely. The same posting without it cannot, however comprehensive the international policy.
This is the mechanism behind the general pattern set out in visa stage versus residence stage health cover: international cover is widely accepted when a visa is issued and rarely accepted once residence is established. Where a genuine residence-stage exemption does exist, it is usually a social security exemption rather than an insurance one.
What an A1 certificate is, and what it does
An A1 is a portable document issued by the social security institution of the country whose legislation applies to a worker — in the Netherlands, for example, the Sociale Verzekeringsbank. It evidences that the worker remains insured in the home system while working in another state, and that contributions therefore continue to be paid there rather than in the host country.
Two things follow, and only the first is obvious. The direct effect is on contributions: the worker and employer keep paying at home. The indirect effect, which is the one that matters for medical cover, is that several countries treat continued home-system membership as a ground for exempting the worker from their own compulsory health insurance. The health insurance exemption is granted by the host state, under its own rules and usually by application to a named authority. The certificate is the evidence, not the exemption.
That distinction explains most of what goes wrong. Holding an A1 does not automatically switch off a host country's enrolment obligation; it establishes the fact on which a host country may, if its rules provide for it, grant an exemption. Where the host country's rules do not provide for it, the certificate settles the contribution question and leaves the enrolment question untouched.
The Netherlands: one of very few genuine exits
Dutch basic health insurance is compulsory for residents and for non-residents who work in the Netherlands and pay Dutch wage tax, and the obligation is to buy the basisverzekering from a Dutch-licensed health insurer. International private cover does not substitute; it can only sit on top. The government's own guidance confirms that the enrolment obligation applies even to people who do not live in the Netherlands and even where they hold foreign health insurance.
Against that background, the genuine exits are narrow, and a posted-worker A1 or certificate of coverage is one of them — alongside the position of staff of international organisations, and short stays that do not trigger municipal registration. There is a four-month window within which cover applies retroactively to the date the obligation arose, which is a grace period for arranging enrolment rather than an exemption from it.
One misconception is worth correcting directly, because it circulates widely among assignees. The Dutch expatriate payroll facility is a tax measure. No official source establishes that it exempts anybody from the health insurance obligation, and it should not be relied on as though it did. The country position is set out in health insurance in the Netherlands for expats.
Switzerland: the most developed exemption framework
Anyone settling in Switzerland must take out health insurance within three months of taking up residence, and the obligation applies irrespective of nationality and to every family member individually. Enrol inside the window and cover is retroactive to the residence date; miss it and cover starts from enrolment, with a premium surcharge unless the delay is excusable. Cantonal authorities administer both exemptions and enforcement, and where a resident fails to insure, the canton assigns them to an insurer.
Switzerland then publishes the clearest set of posted-worker exemptions found anywhere in Europe. Postings from the EU, EFTA and the United Kingdom are exempt for up to two years on the strength of an A1. For India, Japan and North Macedonia, a posting certificate is submitted to the cantonal exemption body. And for states with no agreement at all, an exemption is possible where there would otherwise be a double burden and the existing cover is equivalent for treatment in Switzerland.
That last route is the interesting one, because it puts an international policy directly to the test. "Equivalent for treatments in Switzerland" is a substantive standard, and a plan with a restricted area of cover, a modest annual limit or a large deductible is unlikely to meet it. The Swiss position is covered in health insurance in Switzerland for expats.
The contrast that matters most: partial agreements
The posted-worker logic invites an assumption that is wrong more often than it is right — that where a social security agreement exists between two countries, it exempts the worker from the host system generally.
Social security is not one thing. It is a set of branches — pension, medical, work injury, unemployment, maternity — and totalisation agreements are typically negotiated branch by branch. Mainland China is the clearest published example. Foreigners legally employed there and their employers are required to contribute across all five branches. Advisory sources describing the exemption regime report that nationals of countries with a totalisation agreement are exempt only to the extent of that agreement: German nationals from pension and unemployment only, South Korean nationals from pension only, and medical insurance generally not exempted at all.
Read that in the order an employer experiences it. The agreement exists. The assignee is told they are covered by it. Contributions are structured on that basis. And the one branch that was never within its scope is medical — the branch the employer was most confident about, because it is also the one where the company has bought a comprehensive international plan. Private cover in China is supplementary to the statutory enrolment duty, not a substitute for it, and enforcement varies materially by city. The regional detail is in health insurance in China and Japan for expats, and Japan illustrates the same point in a simpler form: enrolment in public health insurance is compulsory for residents staying beyond a short threshold, regardless of any private or home-country cover held.
International organisations and seat agreements
A parallel exemption exists for staff of international organisations, and it works on a different basis. Rather than remaining in a home national system, the employee is covered by the organisation's own scheme, and the host state disapplies its national social security and health insurance rules under the seat agreement with that organisation. The EU Joint Sickness Insurance Scheme is the best-known example.
Both the Dutch and Swiss frameworks recognise this route explicitly and separately from the posted-worker route. In Switzerland the exemption for diplomats and international-organisation staff turns on whether the organisation's scheme gives equivalent cover for treatment in Switzerland — the same equivalence test applied elsewhere. The practical point for an employer is that the evidence required differs: a seat agreement and proof of scheme membership, not an A1.
The practical mechanics
Who applies, and when. Normally the employer, to the home country's social security institution, before the posting starts. Retrospective issue is possible in many systems but does not reliably cure a host-country enrolment obligation that has already arisen, because those obligations typically run from arrival or registration.
What to apply for on the host side. The certificate is not self-executing. Switzerland requires an application to the cantonal exemption body; the Netherlands operates the exemption through the insured-circle rules rather than automatically. Establish which host authority grants the exemption, what it wants to see, and how long it takes — before departure, not after.
Extensions. Permitted periods are finite. Where a posting runs beyond one — Switzerland's published limit for EU, EFTA and UK postings is two years — either an extension is agreed between the competent institutions or the worker falls into the host system, usually with contributions due from the date the exemption lapsed. Assignments that are extended informally are the most common route from compliance to non-compliance.
Paying twice. The exposure is real and it sits in the gap. If host-country enrolment has already been triggered while home-country contributions continue, both are payable for the overlap, and unwinding the wrong one is a claim rather than an automatic reversal. Deadlines run in parallel with the paperwork: three months in Switzerland, four months in the Netherlands, and enrolment windows measured in days after address registration elsewhere. Budget for the overlap rather than assuming it will be netted off.
Where an exemption does not exist. The programme design question becomes stacking rather than substitution: compulsory local enrolment as the base, with international cover above it for the benefits, networks and portability the local scheme does not provide. That is the same conclusion reached for the Gulf in admitted versus non-admitted insurance, and it belongs in the employer's funding and governance decisions set out in captives, self-funding and multinational pooling.
Verification, and a necessary caution
The framework above is drawn from the published explanatory material of the national authorities concerned. Several of the underlying primary texts could not be read directly during research — including the Swiss ordinance article governing exemptions — so article-level citations should be verified against the ordinance or statute itself before being relied on in any filing or advice. The Chinese exemption detail comes from advisory commentary rather than from a government publication, and should be confirmed with the relevant local bureau, particularly given how much enforcement varies between cities.
Social security coordination rules, bilateral agreement scope and host-country enrolment deadlines all change, and they change without much publicity. Confirm the current position with the home country's social security institution and the host country's competent authority before a posting starts, and again if it is extended. Nothing here is legal, tax or immigration advice. Related employer obligations at the point of arrival are covered in health insurance requirements for visas, and the position when a posting ends is covered in leaving your employer's medical scheme.
Frequently asked questions
What is an A1 certificate?
A portable document issued by the social security institution of the country whose legislation applies to a worker, evidencing that the worker remains insured in that home system while working in another state. Within the EU, EEA, Switzerland and, under the current arrangements, the United Kingdom, it is the standard proof that home-country social security continues to apply. It is issued to the employer or worker on application before the posting, and it is a statement about which system applies rather than a health insurance policy.
Does an A1 exempt me from local health insurance?
In some countries, yes, and that is precisely its value. The Netherlands treats a posted-worker certificate as one of the few genuine routes out of the compulsory basic insurance. Switzerland exempts posted workers from the EU, EFTA and the UK for up to two years on an A1. But the exemption is granted by the host country under its own rules, usually by application to a named body, and holding the certificate is the evidence rather than the exemption itself.
Do social security agreements cover health insurance?
Often not, and this is the most consequential misunderstanding in the area. Totalisation agreements are frequently partial, covering only named branches of social insurance. Advisory sources describing the position in mainland China report that nationals of agreement countries are exempt only to the extent of the agreement — German nationals from pension and unemployment only, South Korean nationals from pension only — and that medical insurance is generally not exempted at all. An employer assuming a blanket exemption will be wrong about the branch that matters most.
Who applies for the certificate, and when?
Normally the employer, to the social security institution of the home country, before the posting begins. Applying late is common and is a problem, because host-country enrolment obligations run from arrival or from registration rather than from the date the certificate is eventually issued. Where an exemption from local health insurance depends on the certificate, a delay can leave a period during which contributions are legally due locally even though the certificate is later granted.
What happens if the posting is extended?
The exemption is time-limited and the extension has to be applied for, not assumed. Switzerland's published position exempts posted workers from the EU, EFTA and the UK for up to two years. Beyond a permitted period, either an extension must be agreed between the competent institutions or the worker falls into the host system. Assignments that quietly roll on past their original end date are the single most common way a compliant posting becomes a non-compliant one.
What is the risk of paying twice?
Real, and usually borne while an exemption is unresolved. If the host country's enrolment obligation has already bitten and the home country's contributions are still running, both are payable for the overlap, and recovering the wrong one is an administrative process rather than an automatic correction. Countries also apply their own deadlines — Switzerland requires insurance within three months of taking up residence, the Netherlands applies a four-month window with retroactive effect — so the clock runs while the paperwork is pending.
Do staff of international organisations need an A1?
Usually not, because their position rests on a different basis. Staff of international organisations are commonly exempted from national social security and health insurance under the organisation's seat agreement with the host state, with cover provided by the organisation's own scheme — the EU Joint Sickness Insurance Scheme being the best-known example. Both the Netherlands and Switzerland recognise this route separately from the posted-worker route, and the evidence required is different.
This guide is general information only and does not constitute financial, legal, medical or tax advice. Global Investments is not authorised by the Financial Conduct Authority. Insurance products, benefit schedules and premiums are revised regularly, and mandatory health insurance requirements change frequently — in several jurisdictions they are described differently even between official sources. Nothing here is a recommendation of any product or insurer. Confirm the legal position with the relevant regulator or a locally qualified adviser, and confirm cover terms with the insurer, before acting.