A commissioning team is booked, the site is ready, and the first technician cannot start because the A1 certificate is still with the home-country institution. Delays like this rarely come from the engineering. They come from treating a cross-border posting as a travel booking instead of a compliance event. For HR and mobility leaders running project workforces in Europe, the question is not only who can travel. It is under which legal regime each engineer works, who owns each filing, and in what order the filings must happen. The rules for that order are about to tighten.
Three regimes decide how an engineer can work in another EU country
Posting
An employee of a company established in one EU or EEA country is sent to deliver a service in another; the employment contract stays with the home employer, and the employee generally stays in the home social security system.
Local employment
The engineer is employed under a host-country contract, either through a local entity or through an Employer of Record; payroll, tax and social security follow the host country.
Third-country nationals
An engineer who is not an EU or EEA citizen needs a valid right to work for the route chosen; whether a posting is possible depends on the immigration status and on the host country's rules, so the route has to be confirmed before the move is planned.
Posting is usually the fastest fit for short, defined deployments. Local employment is usually the safer fit when the project runs long or the team will be embedded on site.
What a posting requires from the employer
Posting declaration
Before or at the start of the posting, the employer notifies the host country's authorities: the employer's identity, number of posted workers, workplace address, expected start and end dates, type of service and a contact person. Any change such as a cancelled or interrupted posting must also be notified.
A1 certificate
The employer requests a Portable Document A1 from the home country's social security institution and informs the host country; the worker stays covered at home and does not build host-country pension or unemployment rights during the posting. If the posting runs beyond two years, the worker either moves into the host system or the employer seeks an extension, which needs agreement between the two countries' authorities.
Host-country working conditions
Host-country terms apply where they are more favourable than the home terms, covering pay, overtime, travel and lodging allowances, maximum working hours, rest periods, paid annual leave, health and safety, and employer-provided accommodation. Under Directive (EU) 2018/957, which Member States had to apply from 30 July 2020, postings longer than 12 months bring most host-country terms into play, extending to 18 months where the employer notifies the host authorities with reasons.
A working checklist for project deployments
| Step | Owner | When |
|---|---|---|
| Confirm the route: posting or local employment | Mobility and legal | Before the project plan is fixed |
| Confirm right to work for each engineer | Immigration | Before travel is booked |
| File the posting declaration in the host country | Employer or provider | Before or at the start of work |
| Request the A1 certificate | Tax and payroll | Before work starts |
| Check host-country pay, allowances and accommodation rules | HR and payroll | Before the contract is issued |
| Diary the 12-month, 18-month and 24-month marks | Mobility | At deployment kick-off |
The last row is the one teams forget. Project end dates slip, and a posting planned for ten months can quietly cross 12.
What the new social security rules change
On 28 September 2026 the Council of the EU gave its final approval to the revised social security coordination rules. The regulation enters into force on the first day of the month after its publication in the Official Journal. At the time of writing, that publication date has not been confirmed.
For posted workers, commentary published since adoption points to a shift from filing after the fact to having the A1 paperwork in place before work starts. It also reports that employees recruited specifically for a posting may need around three months of prior social security coverage in the sending country, and that the new applicable-legislation rules apply roughly 24 months after entry into force. Employers should confirm each of these points against the published text. Until the new rules apply, the current rules remain in force. The practical advice is to use the transition period to change process, not to wait.
What this means for your team
Three changes are worth making now.
- Move the A1 check to the start of the approval workflow.
- Screen new hires before they are slotted into a posting.
- Name one owner. Mobility, payroll, tax and project management each hold part of the file. Without a single owner, the declaration and the A1 move at different speeds.
At xpath.global, our team handles A1 certificates, tax assessment on posting and secondment contracts, and monthly tax calculation and filing, and manages the full assignment lifecycle across immigration, tax, employment and relocation. Where a posting is not the right fit, we run compliant local employment through our Employer of Record service, so a project can start without a new entity in each country.
Plan your project workforce across immigration, tax, employment and relocation with xpath.global.
Assess your workforce deploymentRelated employer guides
- International Workforce Deployment: An Employer Guide to Mobilising Project Teams
- EU Adopts A1 Reform: The Social Security Checklist for Postings in Europe
