A Warsaw-based logistics company operated a fleet of drivers employed under Polish contracts. Those drivers regularly crossed into Germany, the Czech Republic, and Slovakia – sometimes for a single day, sometimes for two weeks at a stretch. The company's HR team assumed that because the drivers were Polish nationals employed by a Polish entity, no social security documentation was required. That assumption cost the company a six-figure correction in retroactive ZUS contributions and triggered an audit by the Social Insurance Institution (Zakład Ubezpieczeń Społecznych, ZUS).

An A1 certificate confirms which country's social security legislation applies to a worker posted abroad. Under EU coordination rules, a worker temporarily sent by a Polish employer to perform services in another EU or EEA member state must hold a valid A1 certificate before departure. Without it, the host country may claim social security contributions for the entire posting period – sometimes retroactively covering 24 months or more. The certificate is issued by ZUS upon application by the employer.

This case study examines how a Polish employer in a structurally common situation – posting workers from Poland to other EU states – ended up in a compliance crisis, how the matter was resolved, and what practical lessons apply to any business with a mobile workforce. The analysis covers the background, the legal strategy deployed, the procedural steps taken, and the transferable conclusions for employers across manufacturing, transport, and professional services.

What went wrong – and why the "Polish employer" assumption fails?

The client operated in road transport, a sector where cross-border movement is routine and documentation requirements are often misunderstood. The company employed roughly 80 drivers. None held A1 certificates. The HR team relied on a single piece of reasoning: the workers were employed in Poland, paid in Poland, and subject to Polish ZUS contributions. That reasoning is factually incomplete.

EU Regulation 883/2004 on the coordination of social security systems does not ask where the employment contract is signed. It asks where the work is physically performed. A driver spending 40 percent of working days in Germany is not automatically covered by Polish social security for those days. The host-country social security authority – in Germany, the Deutsche Rentenversicherung – may claim contributions for each unprotected day. Retroactive claims can reach back 24 months. In this case, the exposure exceeded PLN 380,000 across three host jurisdictions.

A secondary issue compounded the problem. The company had never registered as a "posting employer" with ZUS. This registration is a prerequisite for the A1 application. Without it, even a last-minute attempt to obtain certificates would fail. The employment lawyer Warsaw-based team brought in to assist found that the company lacked both the procedural standing and the underlying payroll documentation needed to support retroactive applications.

  • No A1 certificates issued for any cross-border driver
  • No posting-employer registration with ZUS
  • Incomplete records of days worked per jurisdiction
  • No internal policy distinguishing domestic from cross-border assignments

The ZUS audit was triggered by a whistleblower Poland referral – a former dispatcher who reported the gap to the Social Insurance Institution directly. That channel, available under Polish administrative law, accelerated the timeline significantly. The company received a formal notice within 14 days of the report.

How was the legal strategy structured?

The immediate priority was to stop the accrual of further liability. Every additional day a driver crossed a border without an A1 certificate added to the exposure. The team filed an emergency posting-employer registration with ZUS within 48 hours of engagement. Simultaneously, the team began reconstructing the historical record of cross-border activity from tachograph data, fuel receipts, and GPS logs – the only reliable sources available given the absence of formal posting documentation.

We secured a reduction of the retroactive ZUS surcharge from PLN 380,000 to approximately PLN 210,000 for this logistics client in the Mazowieckie region (autumn 2025). The reduction was achieved by demonstrating that a material portion of the disputed days fell within the 25 percent domestic-activity threshold under EU coordination rules – meaning Polish social security coverage was legitimate for those periods without a separate A1 certificate.

The strategy rested on three pillars. First, accurate jurisdictional mapping: identifying precisely how many days each driver spent in each host country, month by month. Second, threshold analysis: applying the rule that a worker who performs at least 25 percent of their working time in the state of employment retains coverage under the home-state scheme for all postings. Third, prospective compliance: implementing an A1 application workflow before the audit concluded, to demonstrate good-faith remediation to ZUS.

This approach matters beyond the immediate case. For any employer with posted workers, the difference between a defensible position and full retroactive liability often comes down to documentation quality. Tachograph records saved this client roughly PLN 170,000. For a related cross-border analysis involving UK-based postings, see our article on posted workers from the United Kingdom to Poland and A1 certificates.

What did the process look like in practice?

The procedural timeline ran across approximately four months. Week one focused on the emergency ZUS registration and an internal audit of all driver assignments over the preceding 24 months. The team identified 78 drivers with cross-border activity and segmented them into three groups: those with sufficient domestic activity to qualify for the 25 percent threshold, those requiring retroactive A1 applications, and those where the posting period had already expired and only a settlement approach remained viable.

ZUS processed the emergency posting-employer registration within 7 working days. Retroactive A1 applications – covering periods where documentation supported the claim – were filed in batches over weeks three through six. ZUS has a statutory obligation to issue or refuse an A1 certificate within 30 days of a complete application. For contested cases, the timeline extends. Three drivers' applications were initially refused on the grounds that their domestic activity fell below the 25 percent threshold in the relevant months. Those refusals were appealed with supplementary tachograph evidence. Two were ultimately approved; one remained disputed and proceeded to a bilateral coordination process between Polish and German social security authorities.

Our team obtained interim protection against enforcement of the contested German claim for a period of 6 months while the bilateral procedure ran. That protection prevented asset attachment proceedings against the company's vehicles – a step the German authority had signalled it intended to take. For context on how personal liability can arise in parallel tax and social security enforcement scenarios, see our analysis of board liability for tax arrears.

The company also implemented a forward-looking compliance structure. This included a monthly A1 tracking dashboard, a pre-departure checklist for all cross-border assignments, and a designated HR contact for ZUS correspondence. The EU Blue Card and work permit Poland questions that arose for two non-EU national drivers employed by the same company were handled separately but concurrently, avoiding a second compliance gap.

What lessons apply to employers with mobile workforces?

The core lesson is structural: A1 certificates are not a formality reserved for long-term postings. A single day of work performed in another EU member state by a Polish-employed worker can trigger the obligation. Transport, construction, IT consulting, and professional services firms all face this exposure. The posted workers Poland framework applies regardless of the worker's nationality – it applies because of where the employing entity is registered and where the work is performed.

What to prepare before any cross-border assignment:

  • Posting-employer registration with ZUS (one-time, but must precede any A1 application)
  • Records of working days per jurisdiction for each employee (tachograph, calendar, or project logs)
  • Analysis of the 25 percent domestic-activity threshold for each worker
  • A1 applications filed at least 5 working days before the posting begins
  • Internal policy distinguishing domestic assignments from cross-border ones

A second lesson concerns the whistleblower channel. The whistleblower Poland mechanism under Polish administrative law – and its EU-law counterpart under Directive 2019/1937 – means that internal compliance gaps are increasingly reported externally before the employer is aware of them. A retroactive audit is always more expensive than a prospective compliance programme. The cost of the A1 workflow this company implemented going forward is a fraction of the PLN 210,000 it paid to resolve the past exposure.

For employers operating in Slovakia or managing cross-border assignments within Central Europe, the compliance considerations are closely analogous. Our separate analysis of employment law compliance for Slovakia companies in Poland addresses the mirror-image scenario.

A third lesson applies to board members specifically. Where ZUS surcharges remain unpaid, Polish insolvency and corporate law allows enforcement against individual directors personally. That risk is not theoretical – it materialised in a related matter handled by this firm in the same sector. Addressing the social security exposure at the employer level is always preferable to allowing it to reach the threshold where personal liability becomes live.

The final observation concerns the EU Blue Card and work permit Poland dimension. Companies that employ non-EU nationals alongside Polish nationals in mobile roles face a layered compliance obligation: immigration status, work authorisation, and social security coordination must all be verified before each cross-border assignment. Treating these as separate HR silos – rather than an integrated pre-departure check – is the single most common structural failure this firm encounters in transport and construction mandates.

For a tailored strategy on A1 certificate compliance and posted-worker documentation, reach out to info@kordeckipartners.com.

Frequently asked questions

Q: Does a Polish employer need an A1 certificate for a worker sent abroad for just one day?

A: Yes. EU coordination rules do not set a minimum duration for the posting obligation. A single day of work performed in another EU or EEA member state triggers the requirement. The Social Insurance Institution issues A1 certificates upon application, and the application should be filed before the worker departs. Failure to hold a valid certificate for even a short posting exposes the employer to host-country social security claims for that period.

Q: How long does ZUS take to issue an A1 certificate, and what is the cost?

A: ZUS is required to issue or refuse an A1 certificate within 30 days of receiving a complete application. There is no fee for the certificate itself. However, the employer must already be registered as a posting employer with ZUS before applying – that registration step is often overlooked and adds at least 7 working days to the timeline. Employers should build a minimum 5-working-day buffer before any planned cross-border assignment.

Q: Can an employer retroactively obtain A1 certificates to cover past postings?

A: Retroactive applications are possible but are not guaranteed to succeed. ZUS will assess whether the substantive conditions for coverage – including the 25 percent domestic-activity threshold – were met during the historical period. Supporting documentation, such as tachograph records, GPS logs, or project timesheets, is essential. Without contemporaneous evidence, retroactive applications are frequently refused, leaving the employer exposed to the full retroactive claim from the host-country authority.

About KORDECKI & Partners

KORDECKI & Partners is a law firm based in Warsaw and Krakow, advising business clients across 30 jurisdictions. Our team combines expertise in Polish and international law with a practical approach to employment compliance, posted-worker documentation, and cross-border workforce management. We work with Polish entrepreneurs, foreign investors, and in-house legal teams. To discuss your situation, contact info@kordeckipartners.com.

Disclaimer: This publication is provided for informational purposes only and does not constitute legal advice. The information herein should not be relied upon as a substitute for professional legal counsel tailored to your specific circumstances. KORDECKI & Partners assumes no liability for actions taken or not taken based on the contents of this material. For advice regarding your particular situation, please contact info@kordeckipartners.com.