What the UK-Germany Rule Actually Does
The UK and EU coordinate social-security coverage so that a worker in a cross-border situation is generally subject to the social-security legislation of one country at a time. The normal rule is linked to where the work is carried out, but the UK-EU Trade and Cooperation Agreement contains a detached-worker exception for eligible temporary postings.
Germany participates in the detached-worker arrangements under the TCA. For an eligible UK employee sent temporarily from the UK to Germany, the detached-worker rule can allow UK National Insurance legislation to continue for a maximum period of 24 months. HMRC must issue the certificate of coverage (also referred to as a PDA1/A1 certificate) for the worker to rely on UK National Insurance coverage and use the certificate as evidence that German social-security contributions are not payable for the covered period.
Key 2026 Rules
| Issue | Current rule |
|---|---|
| Main framework | UK-EU Trade and Cooperation Agreement, Protocol on Social Security Coordination |
| Normal principle | Workers are generally subject to one country's social-security legislation, normally linked to where work is performed |
| Detached-worker period | Up to 24 months where the applicable conditions are satisfied |
| UK evidence | HMRC certificate of coverage (PDA1/A1) |
| UK employee application | HMRC CA3822 for temporary work in an EU country |
| Self-employed temporary work | Separate HMRC CA3837 process |
| Tax and immigration | Separate from social-security coordination |
When Can a UK Employee Stay in the UK National Insurance System?
The detached-worker route is designed for a worker who normally works in one country for an employer established there and is temporarily sent by that employer to work in the other country. For the UK-to-Germany scenario, the UK employer should normally carry out its activities in the UK and the employee should be sent to Germany to work on that employer's behalf.
The 24-month limit is not the only condition. The detached-worker rule also requires the sending employer to normally carry out its activities in the UK, the employee to be sent to Germany to perform work on that employer's behalf, and the worker not to replace another detached worker. People who normally work in several countries, work for different employers, or change employer during the assignment can fall under different rules. The facts must therefore be checked rather than treating every UK-to-Germany assignment as automatically covered.
How to Obtain the UK Certificate
HMRC's CA3822 process is used to apply for a certificate confirming that an employee working temporarily in an EU country continues to pay UK National Insurance. Germany is within the EU countries covered by this process.
Before applying
The employer must have confirmation from HMRC that its business is eligible to apply for certificates using the process.
The application requires information such as the worker's identity and nationality details, the employer's PAYE reference and details of the overseas assignment.
When to apply
HMRC's CA3822 guidance says an application cannot be made more than 12 months in advance. The application should be made before the assignment where possible so that the worker has evidence of the applicable social-security legislation.
After approval
The certificate demonstrates to the host country that UK National Insurance legislation applies. Where the conditions are met, HMRC may also issue an S1 healthcare entitlement certificate for a worker resident in an EU country.
What Happens at 24 Months?
The 24-month detached-worker rule is a maximum period for the ordinary exception. If the assignment is expected from the outset to last longer than 24 months, the normal detached-worker rule cannot simply be used for the entire assignment.
If an assignment unexpectedly extends beyond 24 months, the applicable legislation needs to be reconsidered from the point at which the detached-worker conditions cease to apply. A separate exception agreement can sometimes allow the sending state's legislation to continue, but this requires the competent authorities to agree; it is not an automatic extension of the A1 certificate.
A1 Does Not Solve Every Germany Compliance Issue
| Issue | Does the A1 certificate decide it? |
|---|---|
| UK National Insurance vs German social security | Yes — this is its core purpose |
| German income tax | No |
| UK income tax | No |
| German work/residence permission | No |
| German posted-worker notification or labour-law duties | No |
| Healthcare entitlement | Related certificates such as S1 may be relevant where the conditions are met |
Frequently Asked Questions (6)
Official 2026 Sources
- • HMRC — CA3822: UK National Insurance certificate for temporary EU work
- • HMRC — UK/EU social security guidance: National Insurance when working in the EU
- • European Union — UK TCA: Trade and Cooperation Agreement
- • German social-security authority: GKV-Spitzenverband / DVKA
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2026 Quick Reference
Important Distinction
A certificate of coverage confirms the applicable social-security legislation. It does not prove that the worker has the right to enter or work in Germany and does not determine where employment income is taxable.