Ask most HR or finance teams about Certificate of Coverage social security compliance for international assignments and you will hear one of two things.
Either: “we handle that through payroll.” Or: “we have an A1 for EU travel.”
Both answers are incomplete.
And in a significant number of cross-border situations, neither applies at all.
The Certificate of Coverage — often abbreviated to CoC — is the instrument that sits at the centre of international social security compliance for movements outside the European Union framework.
It is not widely understood. It is routinely obtained too late. And when it is missing, the consequences range from double social security assessments to failed benefit claims — and, in US-centric situations, a FICA dispute that ends up in front of a court.
This article is written for businesses, employees and self-employed individuals dealing with cross-border assignments that fall outside the EU/EEA — movements between the UK and the US, between the US and Japan or Australia, between the UK and Canada, and so on.
If your mobility programme primarily involves intra-European assignments, our dedicated article on the A1 certificate and short business trips in Europe covers that framework in depth. Here, we focus on the wider world.
The mental model most organisations apply to social security compliance goes roughly like this: the employee is on home-country payroll, contributions are being deducted, and the compliance question is therefore settled.
For domestic employees, that is entirely correct.
The moment an employee crosses a border to work — even temporarily — the picture changes.
Social security law in most jurisdictions is territorial.
Contributions are in principle owed where the work is physically performed.
The existence of a home-country payroll deduction does not cancel the host country’s claim.
It simply means both countries now have a plausible basis for demanding contributions on the same earnings.
The Certificate of Coverage exists to resolve exactly this conflict.
It is the official document through which the home-country authority certifies to the host country that the worker is already covered — and that the host country should therefore not assess its own contributions.
Without it, the legal protection most employers assume they have does not exist. Even when every penny of home-country contribution is being paid correctly.
What makes the CoC distinct from the EU’s A1 certificate is the legal machinery behind it.
The A1 operates under EU Regulation 883/2004 — a directly applicable framework across all member states.
The Certificate of Coverage, by contrast, operates under individual bilateral totalization agreements — separately negotiated treaties between two specific countries.
The rules vary by country pair. The issuing authority differs. And the application process is not standardised across a single framework.
A totalization agreement — sometimes called a bilateral social security agreement or reciprocal agreement — is a social security insurance treaty between two countries designed to do two things.
First, prevent the same earnings from being subject to social security contributions in both countries simultaneously.
Second, allow workers to combine periods of contribution from both countries to establish benefit entitlement — particularly for retirement.
As of 2026, the United States has 30 active totalization agreements.
They cover countries including the United Kingdom, Australia, Canada, Japan, South Korea, Switzerland, and most of Western Europe.
The UK similarly has its own network of reciprocal agreements with non-EU countries.
Where an agreement is in force, the Certificate of Coverage is the mechanism by which its protection is activated. It is not automatic.
This last point is critical, and it is where most international assignments hidden compliance risks begin.
Having a totalization agreement in place between two countries does not, by itself, protect anyone from double contributions.
A US employer sending a worker to Australia under the US-Australia agreement is only protected from Australian social security contributions if they have requested and received a Certificate of US Coverage from the SSA. The agreement is the framework. The certificate is the key.
For country pairings where no totalization agreement is in force — and there are many — the exposure is more acute.
Popular assignment destinations including China, India, Singapore, the UAE, and most of the Gulf states have no totalization agreement with either the US or the UK (it was only in February 2026 that the India-UK agreement on Social Security relating to Social Security Contributions was signed).
An employee posted to China from a UK employer, or from a US employer to India, faces the prospect of mandatory host-country social security contributions on top of whatever the home country requires.
There is one important UK-specific domestic rule worth flagging here.
Under UK domestic legislation, a UK employer sending an employee to work in a country with which the UK has no reciprocal social security agreement is still required to continue paying UK National Insurance contributions for the first 52 weeks of that overseas assignment. The employee similarly remains liable for NIC during that initial period.
After 52 weeks, the UK NIC obligation falls away — but by that point the host-country social security question will almost certainly have crystallised in its own right, and local registration may be required.
The 52-week rule is a domestic grace period. It is not a long-term compliance solution, and it does nothing to address what the host country may simultaneously be requiring.
The mirror image applies on the inbound side.
A foreign national arriving in the UK from a country with which the UK has no social security agreement is exempt from UK NIC for their first 52 weeks of UK employment.
This is a meaningful relief for short-term inbound assignees — it avoids an immediate UK NIC liability on top of contributions continuing at home. But it is time-limited and must be tracked carefully.
Employers who allow the 52-week window to lapse without reassessing the position can find themselves with an unexpected NIC liability arising at the anniversary.
For UK employers, HMRC publishes guidance on countries with which the UK has reciprocal social security agreements.
For US employers, the SSA’s Office of International Programs maintains the definitive list of totalization agreements and applicable rules by country pair.
It is worth checking both before making any assumptions.
There is consistent confusion, particularly in HR and payroll teams, about the exact scope of a Certificate of Coverage. The following distinctions matter in practice.
The intersection between social security compliance and the broader set of cross-border obligations — income tax, payroll withholding, shadow payroll, permanent establishment — is a recurring source of unexpected costs.
Our guide to moving to the UK from the USA explores how these obligations interact in practice in the example of someone being sent on assignment from the US to the UK.
The following situation is representative of what we encounter with reasonable regularity in organisations expanding internationally for the first time, or that have grown quickly without formalising their global mobility compliance processes and policies. Details have been changed.
A US-headquartered technology company expands its sales operation into Japan.
However, rather than establishing a local entity immediately, it assigns two senior sales managers — both US nationals, both on US payroll — to spend the better part of a year developing the client base on the ground in Tokyo.
The assignment is projected to run eleven months.
The company’s HR team registers both assignments on its HR system.
Payroll continues as normal: US federal and state income tax withheld, FICA deducted at the standard rate.
Nobody raises the Japan social security question.
The company’s payroll provider is US-based and processes US payroll correctly.
There is no Japan-specific adviser in the picture.
The company begins setting up a Japanese subsidiary.
A local employment law adviser reviews the employees’ time in Japan.
The adviser notes that under Japanese social insurance law, both employees have been working in Japan for over nine months without registering for Japanese health insurance and pension coverage — registrations that would normally have been triggered from the first month of employment.
The US-Japan totalization agreement covers pension contributions.
Had the company obtained a Certificate of US Coverage from the SSA before the assignment started, the pension contribution obligation in Japan would have been eliminated.
The US FICA deductions being made all along would have served as the sole pension-related obligation.
But without the certificate, they carry no weight in Japan.
The pension exposure — backdated across nine months for two employees — generates a retrospective assessment.
Late registration also triggers administrative penalties under Japanese social insurance law.
The Certificate of Coverage application to the SSA takes approximately six to eight weeks to process.
Had it been submitted before the employees boarded their flights, the pension component of the Japan liability would never have arisen.
The health insurance piece would still have needed to be managed separately — but that too is a known quantity when you approach an assignment with the right framework from the outset.
The total cost of the retrospective assessment and penalties ran to roughly five times what proactive advice and a timely application would have cost.
It also complicated the subsidiary set-up process and left both employees uncertain about their Japanese benefit entitlements for the period in question.
The company now has a pre-departure checklist and assignment management process in place that includes a Certificate of Coverage assessment as a standard step for every international assignment — not just those going to totalization agreement countries, but all assignments.
The question is always asked. The answer is always documented.
Japan is a useful example because it illustrates both the benefit of the US-Japan totalization agreement and its limits.
For a fuller picture of what a Japan posting involves from a compliance perspective, our guide on moving to Japan on an intra-company transfer covers the full framework.
The application process varies depending on which country’s system is assigning coverage.
The most common scenarios in a global mobility context involve US and UK employers, so we address both.
The Social Security Administration’s Office of Earnings and International Operations handles Certificate of Coverage requests for US workers.
Applications are submitted online via the SSA’s Certificate of Coverage request portal, which replaced the older mail and fax process.
Online submission is faster, includes data validation checks, and provides email confirmation once the request is approved.
The information required typically includes:
Processing times have historically run between four and eight weeks (though at times it may have taken longer).
The SSA advises applying before the foreign work begins.
As of late 2025, the SSA has transitioned to Login.gov or ID.me for portal identity verification.
Legacy login credentials no longer work for the online system.
For US employers sending workers to foreign affiliate entities, there are additional procedural considerations.
The SSA publishes country-specific guidance for each totalization agreement via its International Agreements page.
Italy’s agreement, for example, operates under materially different rules from the standard framework.
For UK-based workers posted to non-EU countries with which the UK has a reciprocal agreement, the Certificate of Coverage application is made to HMRC.
For most employed workers and self-employed individuals, the relevant form is CA9107 — covering assignments to countries such as the US, Canada, South Korea, and Japan.
For self-employed workers working temporarily in an EU country, Gibraltar, Iceland, Liechtenstein, Norway or Switzerland, the equivalent is form CA3837.
HMRC’s process went through significant changes following Brexit, with postal forms progressively replaced by digital versions submitted via Government Gateway.
Processing times can vary. As with the SSA, applying before the assignment starts is strongly advisable — not merely best practice.
A certificate issued after the work has already begun creates a gap period for which no formal protection is in force.
HMRC’s guidance on social security abroad — published under reference NI38 — remains the primary reference for UK nationals working abroad.
It covers the interaction between UK National Insurance obligations and foreign social security systems across both agreement and non-agreement countries.
The Certificate of Coverage has a specific interaction with US federal tax compliance that surprises some employers.
Under IRS guidance on totalization agreements, a worker claiming exemption from FICA because of a totalization agreement must be able to produce a Certificate of Coverage from their home-country authority.
Revenue Procedures 80-56 and 84-54 — and Revenue Ruling 92-9 — all reinforce this requirement.
A US court ruling in Bond v. United States made this explicit: the totalization agreement alone is not self-executing.
The FICA exemption is only valid when the certificate has actually been obtained.
An employer who stops deducting FICA from a foreign national’s US payroll — relying on the existence of a totalization agreement without holding a certificate — is exposed to back FICA assessments if the position is challenged.
The practical implication for US employers is straightforward: retain the Certificate of Coverage in the payroll file.
It should not routinely be sent to the IRS, but it must be produced immediately if the IRS requests it during an audit.
Self-employed individuals are in a slightly different position.
They should attach a copy of the certificate to their US tax return for the relevant year.
This question comes up often, and it reflects a genuine ambiguity in how the terminology is used.
The A1 certificate is the specific document used under EU Regulation 883/2004 — applicable to movements within the EU, EEA, and Switzerland.
It operates under a unified regulatory framework that applies consistently across all member states.
The A1 is, in effect, the EU’s version of a Certificate of Coverage.
The Certificate of Coverage — or CoC — is the broader term for the equivalent document issued under bilateral totalization agreements outside the EU.
When a UK employer sends a worker to the US, the relevant instrument is a Certificate of Coverage issued by HMRC, confirming continued NIC coverage.
When a US employer sends a worker to the UK, the US Certificate of Coverage issued by the SSA serves the equivalent purpose.
The two systems sit side by side for organisations operating across both EU and non-EU territories.
A UK global mobility programme that includes assignments to both Germany and Canada, for example, needs A1 applications for the German movement and Certificate of Coverage applications for the Canadian one — under different application forms, different timelines, and different procedural rules.
Post-Brexit, the UK no longer sits within the EU coordination framework for movements between the UK and EU member states.
UK workers going to EU countries now need A1 certificates issued by HMRC under the UK-EU social security provisions in the Trade and Cooperation Agreement.
Our article on remote working across borders post-Brexit explores how this affects both employers and employees.
A Certificate of Coverage (CoC) is an official document issued by the social security authorities of a worker’s home country.
It certifies that the worker is covered under the home country’s social security system during a period of temporary work abroad.
It provides the legal basis for exempting the worker and employer from paying social security contributions in the host country on the same earnings.
In the EU context, this document is called an A1 certificate.
Outside the EU — under bilateral totalization agreements — it is referred to as a Certificate of Coverage.
The Certificate of Coverage is issued by the social security authorities of the country whose system is assigning coverage — the country where the worker is home-based and continues to contribute.
For US workers, it is issued by the Social Security Administration (SSA).
For UK workers, it is issued by HMRC.
For workers from other countries, the issuing authority is the relevant national social security body in their home country.
For instance, INPS in the case of an Italian Certificate of Coverage.
US employers and self-employed individuals can apply online through the SSA’s Certificate of Coverage request portal.
You will need: the worker’s Social Security number; details of the US employer; the name and address of the host organisation in the destination country; the country of assignment; and the start and end dates of the foreign work period.
The SSA typically processes applications within four to eight weeks. Apply before the foreign work begins.
In the US context, the relevant instrument is the SSA’s online Certificate of Coverage application, accessed via the Office of Earnings and International Operations portal.
The applicable form and submission address vary by destination country — the SSA’s country-specific pages list the relevant details.
For UK applications, the relevant form is CA9107 for most employed workers being posted outside the EU/EEA, and CA3837 for self-employed individuals within the EU/EEA.
A Certificate of Non-Coverage confirms that a worker is not covered under a particular country’s social security system — typically issued when a worker has been determined to be subject to a different country’s system under the applicable totalization agreement.
It can be requested by an employer or worker to demonstrate to a host-country authority that local contributions are not due.
In practice, the Certificate of Coverage is the more commonly required document.
The Certificate of Non-Coverage arises in specific administrative contexts, often where the host-country authority is questioning whether a worker should be enrolled in its system.
No. In the US context, the Certificate of Coverage issued under a totalization agreement relates to social security contributions under Title II of the Social Security Act — it does not address health insurance.
US totalization agreements explicitly exclude Medicare.
Health insurance for internationally mobile employees is managed through the employer’s global benefits programme, not through the social security compliance framework.
The “Certificate of Coverage” terminology is also used in a health insurance context — for example, as a document issued by an HMO summarising an individual’s plan coverage.
This is a separate instrument entirely, unrelated to the social security compliance document described in this article.
As of 2026, the US has 30 active totalization agreements.
Countries with agreements include: Australia, Austria, Belgium, Brazil, Canada, Chile, Czech Republic, Denmark, Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Japan, Luxembourg, Netherlands, Norway, Poland, Portugal, Slovak Republic, Slovenia, South Korea, Spain, Sweden, Switzerland, United Kingdom, and Uruguay.
The SSA maintains the definitive current list. Notably absent are China, India, Singapore, the UAE, and most of the Gulf states — meaning workers assigned to these locations from the US face potential double contributions without treaty relief.
The UK has reciprocal agreements with a range of non-EU/EEA countries.
Countries with agreements include: Barbados, Bermuda, Canada, Chile, India (as of February 2026), Israel, Jamaica, Japan, Mauritius, New Zealand, Philippines, Republic of Korea, Republics of former Yugoslavia, Turkey and the USA.
Notably absent are Australia, China, Singapore, the UAE, and most of the Gulf states — meaning workers assigned to these locations from the UK face potential double contributions without treaty relief.
This varies by totalization agreement.
Under the US-UK agreement, a US employer can retain a worker under US social security coverage for up to five years.
Under some agreements the initial period is shorter and extensions must be separately negotiated between the two countries’ authorities.
As with the A1 certificate, a CoC should never be allowed to expire during an active assignment without a renewal application already in progress.
Without a Certificate of Coverage, the legal protection offered by the totalization agreement is not activated.
The host-country authority may assess social security contributions on the worker’s earnings for the period of work — in addition to the home-country contributions already being paid.
In the US, failure to hold a certificate when one is required can result in FICA assessments on earnings the employer believed were exempt.
Courts have consistently confirmed that the agreement alone is not sufficient — the certificate must be in hand.
Retroactive applications may be accepted in some jurisdictions. But they are not guaranteed, and they do not remove the exposure for the unprotected period.
Yes. Most totalization agreements include provisions for self-employed workers, and the Certificate of Coverage process is available for the self-employed as well as for employees.
A self-employed person working temporarily in a totalization agreement country can remain covered by their home-country system and use a Certificate of Coverage to evidence that fact to the host country.
The rules differ by agreement — some impose different thresholds or time limits for the self-employed — and the application process in some countries is less streamlined than for employees. But the entitlement exists.
The Certificate of Coverage is a procedural document. The application is not complex. The form is not long. In most cases the SSA or HMRC will process it without difficulty.
The reason organisations find themselves in trouble is almost never the complexity of the instrument itself.
It is the sequence.
The decision to send someone abroad is made. Logistics are arranged. The assignment begins. And the social security question surfaces — if it surfaces at all — several months later, often in response to something going wrong or a retroactive tax assessment.
We see this pattern regularly. The fix is not a more sophisticated HR system. It is asking the right question at the right point in the process: before the employee boards the flight, not after they have been working in the host country for a quarter.
For organisations managing US-UK assignments, the Certificate of Coverage question sits alongside income tax treaty analysis, FICA vs NIC allocation, shadow payroll considerations, and immigration compliance.
The broader picture is set out in our overview of the expatriate management process.
For movements to countries with no totalization agreement, the absence of a Certificate of Coverage framework does not mean the social security question disappears (and if does, like in the case of the UK, it is only for the first 52 weeks).
It means it must be addressed through different mechanisms: local social security registration, employer cost modelling, tax equalisation adjustments, and in some cases permanent establishment analysis.
Our overview of remote working and PE risks is relevant wherever an employee’s physical presence creates obligations beyond the social security question alone.
Cross-border social security compliance rarely fails because organisations don’t care about it.
It fails because nobody is looking at the full picture at the right moment — immigration, income tax, social security, payroll, and PE risk, all together, before the assignment starts.
Not many organisations have the prior experience or cross-disciplinary know-how needed to look at a cross-border social security situation from a 360° angle.
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