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What an A1 Certificate Actually Is
An A1 certificate is the document that states which single country’s social security system you belong to. Under EU rules you are covered by exactly one country at a time and pay contributions in one country only (per the European Commission’s social security coordination rules) — the A1 is the piece of paper that says which one.
That matters more than most developers expect. It is not a tax form and it does not decide your income tax. It decides where your pension accrues, which health system you are insured under, and which country pays if you are made redundant.
TL;DR:
- The A1 says which country’s social security covers you — one country only, never two
- Legal basis: Regulations (EC) 883/2004 and 987/2009, in force since 2010, across the EU plus Iceland, Liechtenstein, Norway and Switzerland
- Telework from your country of residence at 25% to under 50% of your time and you can stay on your employer’s country’s system, via the cross-border telework framework agreement
- Hit 50% and the default flips: your country of residence takes over
- The framework agreement has 23 signatory states as of 1 February 2026, when Estonia joined
- Salaried workers only — self-employed people are explicitly excluded
- Retroactive applications are capped at 3 months
The 50% Line Is the Whole Game
Before July 2023, a cross-border employee could telework from home for at most 25% of their working time before their country of residence took over their social security. The pandemic-era exceptions that suspended this ended in June 2023.
What replaced them is the Framework Agreement on the application of Article 16(1) of Regulation (EC) No 883/2004 in cases of habitual cross-border telework, drafted by the EU’s Administrative Commission for the Coordination of Social Security Systems and in force since 1 July 2023. Belgium acts as the depositary state, which is why the Belgian Federal Public Service for Social Security maintains the authoritative list of who has signed.
The agreement raises the ceiling: you may telework from your country of residence for 25% up to but not including 50% of your total working time and remain on your employer’s country’s social security. Cross that 50% line and you fall back to the ordinary rules, where your country of residence becomes competent.
For a developer employed by a company in one country and living in another, that single percentage decides which pension system you are building up in — for years at a time.
Who has signed
23 states are in as of 1 February 2026, when Estonia became the 23rd signatory (per KPMG’s Global Mobility Services alert, February 2026). The original 1 July 2023 cohort includes Austria, Belgium, Croatia, Czechia, Finland, France, Germany, the Netherlands, Poland, Slovakia, Spain, Sweden and Switzerland. Slovenia joined on 1 September 2023 and Ireland on 1 June 2024.
The list changes. Check the Belgian social security register rather than trusting any article’s snapshot — including this one.
The Six Conditions, All of Which Must Hold
Luxembourg’s Centre commun de la sécurité sociale publishes the conditions plainly, and they are cumulative — failing any one drops you out of the framework:
- The activity must be salaried. Self-employed workers are not covered.
- Telework is at least 25% and under 50% of total professional activity.
- Both your employer’s state and your state of residence must be signatories.
- Telework is carried out exclusively in your state of residence.
- You have no other usual activity besides the one for your employer’s state.
- There is a connection to the employer’s IT infrastructure.
Condition 1 is the one that catches people. A large share of remote developers in Europe invoice as contractors rather than sitting on a payroll, and for them this agreement simply does not exist. Conditions 4 and 5 are the ones that catch the well-travelled.
What Happens Below 25%, and What Happens Outside
If your telework is under 25%, or the framework does not apply for any other reason, you are not left without rules — you fall under the ordinary Article 13 “activities in two or more Member States” provisions, and your state of residence determines the applicable legislation.
| Your situation | Which country’s social security | Route |
|---|---|---|
| Telework under 25% of the time | Employer’s state | Ordinary Article 13 pluriactivity rules |
| Telework 25% to under 50% | Employer’s state | Framework agreement, Article 16(1) |
| Telework 50% or more | State of residence | Ordinary Article 13 pluriactivity rules |
| Self-employed, any split | Not covered by the framework | Article 13 applies; seek advice |
| Either state not a signatory | Not covered by the framework | Article 13 applies |
The Mechanics Nobody Reads Until It Is Late
Nothing is automatic. Both the employer and the employee have to apply for the A1. It is issued for a defined period — typically one to three years, and under the framework Luxembourg’s CCSS issues it automatically for the declared period up to a maximum of three years.
Retroactivity is capped at three months. The original transitional window that allowed declarations reaching back to 1 July 2023 closed on 30 June 2024. After that, three months is all you get. If you have been quietly teleworking across a border for a year without paperwork, you cannot simply regularise the whole period.
Changes must be re-declared. Moving country, changing your telework percentage, or picking up a second activity all require a fresh declaration. An A1 describes a situation, not a person, and it stops being true the moment the situation changes.
The genuinely unresolved part: business travel
Here the honest answer is that nobody knows. The framework is built for telework strictly between two countries — your residence and your employer’s. Regular work in a third country is not permitted.
Occasional, unplanned, short business trips elsewhere may be tolerated in practice. But as KPMG notes, there is no legal clarity on how such travel is assessed: it is uncertain when a trip might invalidate or cancel an A1, or knock someone out of the framework entirely. There is no published threshold — no “10 days a year” line to stay under.
If you are the kind of engineer who does two conferences and a customer visit a year, document the travel and get advice before assuming it is fine. Anyone telling you the exact allowance is inventing it.
Coming in the Near Future — But Not Law Yet
In April 2026, EU countries approved revised coordination rules updating Regulations 883/2004 and 987/2009. For anyone posted abroad rather than teleworking, the anti-fraud tightening is the headline: a worker must be insured in their home country for at least three months before being posted; after 24 months of posting there must be a break of at least two months before another posting; and postings must generally be notified in advance.
These are not in force. The European Commission is explicit that the new rules take effect only after the European Parliament and the Council formally adopt them and they are published in the Official Journal. Treat anything you read describing them as current law with suspicion — including any recruiter who quotes them at you.
Why This Belongs on Your Job-Hunt Checklist
A job ad that says “remote, anywhere in Europe” is making a claim about the company’s willingness, not about the legal machinery underneath it. The questions worth asking in a first call are unglamorous and very cheap:
- Which legal entity employs me, and in which country?
- Will you apply for an A1 for me, and who handles it?
- Is my country of residence a signatory to the telework framework agreement?
- What percentage of my time is expected on-site?
An employer with cross-border staff already will answer these in a sentence. An employer that goes quiet has told you something useful.
At Xeito we index remote roles that are genuinely workable from the EU — which means paying attention to where the employing entity actually is, not just what the ad says.
Frequently Asked Questions
Does an A1 certificate affect my income tax?
No. Social security and income tax are separate regimes with separate rules and separate thresholds. An A1 determines only which country’s social security system covers you. Your income tax position is decided under national law and any applicable double-tax treaty, and the two can land in different countries. Do not let anyone conflate them.
I am a freelancer. Can I use the telework framework agreement?
No. The framework agreement covers salaried activity only — self-employed workers are explicitly excluded from it. The ordinary Article 13 rules on activities in two or more Member States still apply to you, so you are not outside the system, but the 25–50% flexibility is not available.
What happens if I telework exactly 50% of the time?
You fall outside the framework. The agreement covers telework of 25% up to but not including 50%, so 50% itself is not within it, and the ordinary pluriactivity rules apply — which generally means your country of residence becomes competent.
Can I get an A1 backdated to cover last year?
Generally no. Retroactive applications are limited to a maximum of three months. The transitional window that allowed declarations back to 1 July 2023 closed on 30 June 2024.
How long does an A1 last?
Typically one to three years. Under the framework agreement the certificate is issued for the declared telework period, up to a maximum of three years, after which it must be renewed.
Do both my employer and I have to do something?
Yes. The application is made by employer and employee together — an A1 is not something the employee can quietly arrange alone, and it is not issued automatically when you start working remotely.
My country is not on the signatory list. What then?
The framework agreement does not apply, and the ordinary Article 13 rules decide the applicable legislation — which for habitual telework from your home usually means your country of residence. Both states must be signatories for the agreement to be available.
Does an A1 let me work from anywhere in Europe?
No, and this is the most common misreading. The framework covers telework between two specific countries: your residence and your employer’s. Regular work from a third country is not permitted, and the treatment of occasional short business trips outside those two is legally unsettled.
Sources
- Belgian Federal Public Service Social Security — Cross-border telework in the EU, the EEA and Switzerland — depositary state’s authoritative signatory list and framework overview.
- Luxembourg CCSS — Framework agreement on telework — the six cumulative conditions, 25%–<50% band, self-employed exclusion, and up-to-3-year A1 validity used in this article.
- KPMG GMS Flash Alert 2026-041 — Estonia Joins European Cross-Border Telework Framework — Estonia signed 13 January 2026, effective 1 February 2026 as the 23rd signatory.
- KPMG GMS Flash Alert 2024-114 — Deadline for A1 Applications for Telework Approaching — 30 June 2024 close of the transitional retroactivity window and the ongoing 3-month cap.
- European Commission — EU social security coordination — Regulations 883/2004 and 987/2009 in force since 1 May 2010, applicable across the EU plus Iceland, Liechtenstein, Norway and Switzerland.
- European Commission — Modernising EU social security coordination rules (30 April 2026) — April 2026 political agreement on the posting-fraud tightening (3-month prior insurance, 24-month posting limit, 2-month cooling-off), pending Parliament and Council adoption.
Looking for a remote role that is genuinely workable from where you live? Xeito indexes EU-workable remote developer jobs and shows you where the employing entity actually sits, so the social security question is answerable before you apply.