Posted workers from Poland to Poland – A1

A Polish IT consultancy sends three developers to a German client's Warsaw office for a six-month project. The developers are employed in Poland, the client entity is registered in Germany, and the work is performed on Polish soil. Does an A1 certificate apply? The answer surprises many employers: yes, in certain configurations, Polish Social Insurance Institution (Zakład Ubezpieczeń Społecznych, ZUS) requires an A1 certificate even when both the employer and the employee are based in Poland.

An A1 certificate confirms which country's social security legislation applies to a worker during a period of posting or multi-state activity. Under EU coordination rules, a worker posted from one employer to a worksite – even within Poland – may require a certificate when the posting involves an international corporate structure, a foreign contracting entity, or cross-border payroll arrangements. ZUS issues the certificate, typically within 25 business days of a complete application. Failure to obtain it where required exposes the employer to personal liability for unpaid contributions and potential administrative penalties.

This guide walks through the full A1 procedure for Polish-based workers in Poland-to-Poland posting scenarios: when the certificate is required, how to apply step by step, the most common errors, and how three different business structures – manufacturing, IT services, and a foreign investor's subsidiary – should approach the process. Employers dealing with multi-state workers, EU Blue Card holders, or workers on work permits in Poland will find the compliance checkpoints especially relevant.

When does the A1 certificate requirement apply to postings within Poland?

The obligation to obtain an A1 certificate arises when the applicable social security legislation is in doubt – not simply when work crosses a geographical border. In Poland-to-Poland posting scenarios, the trigger is typically the international character of the employment relationship rather than the physical location of work. Three configurations generate the requirement most frequently: a Polish subsidiary of a foreign group seconding an employee to another Polish group entity; a Polish employer providing workers to a Polish-registered branch of a foreign company; and a worker already holding an A1 for posting abroad who temporarily returns to Poland mid-assignment.

ZUS applies EU Regulation 883/2004 on the coordination of social security systems and its implementing Regulation 987/2009. Where a Polish employer posts a worker to a Polish entity that is part of a multinational corporate structure, ZUS may treat the arrangement as a cross-border posting if the contracting entity's decision-making centre is abroad. The 24-month maximum posting period under EU coordination rules applies from the start of the assignment, not from the date of any subsequent A1 application.

Practical indicators that trigger the requirement include:

The worker's contract identifies a foreign parent or affiliate as the end client
Payroll or social contributions are being managed from a foreign jurisdiction
The worker holds a work permit in Poland tied to a foreign employer
The worker simultaneously performs duties in more than one EU member state
An EU Blue Card issued in another member state is the basis of the worker's right to work

Employment lawyers in Warsaw see the most disputes arise where employers assume that "everything is in Poland" removes any EU-law dimension. That assumption is wrong when the corporate structure crosses borders – even if the employee never leaves the country. The National Court Register (Krajowy Rejestr Sądowy, KRS) registration of the receiving entity does not, by itself, establish that the arrangement is purely domestic. An employment lawyer in Warsaw advising on posting structures should always map the full corporate chain before concluding no certificate is needed.

What is the step-by-step A1 application procedure in Poland?

The A1 application is filed with ZUS on form US-36 (for posting) or US-35 (for multi-state workers). The employer submits the application electronically via the ZUS PUE platform or by paper to the ZUS branch handling the employer's contribution account. ZUS processes the application within 25 business days of receiving a complete file. If ZUS raises questions or requests supplementary documents, the clock pauses until the employer responds – making completeness on first submission the single most important variable in timeline management.

The core documents for a standard posting application are:

Completed US-36 form with the posting period, receiving entity details, and description of work
Confirmation that the employee has been subject to Polish social security for at least one month immediately before the posting begins
Evidence of the employer's substantial activity in Poland (payroll records, contracts, KRS extract)
Copy of the employment contract or posting agreement identifying the receiving entity
Work permit or EU Blue Card if the worker is a non-EU national

ZUS will verify that the employer conducts "substantial activity" in Poland – meaning that at least some genuinely productive work is performed in Poland beyond purely administrative management. A shell entity with no real Polish operations cannot validly post workers under EU coordination rules. This check has become stricter since 2023, and ZUS increasingly requests payroll tax records from the Polish Tax Authority (Urząd Skarbowy) to cross-reference reported employment numbers.

Once issued, the A1 certificate is valid for the period stated on its face, up to 24 months. If the posting extends beyond that limit, the employer must either apply for an extension (which requires agreement from the competent authority of the other state involved) or restructure the arrangement. Extensions are not automatic. We obtained a timely A1 extension for a manufacturing client in the Mazowieckie region whose 24-month certificate was about to lapse mid-project (autumn 2025) – averting a gap in social security coverage that would have triggered retroactive contribution liability.

What are the most common mistakes employers make with A1 certificates?

The most damaging error is simply not applying. Many Polish employers in multinational groups assume that posting a worker within Poland requires no EU-law documentation. When ZUS or a foreign social security authority later audits the arrangement, the absence of an A1 certificate means the employer cannot prove which country's legislation applied. The result is potential double contributions – one state claiming the worker was subject to its system, another doing the same – plus penalties that can reach PLN 5,000 per violation under Polish social insurance law.

The second major error is applying too late. The A1 certificate should be in place before the posting begins, not after. ZUS can issue certificates retroactively in some cases, but retroactive issuance requires a compelling explanation and is not guaranteed. An employer who applies after an audit has already started forfeits the procedural protections that an advance certificate provides. This is the irreversible consequence that makes late applications so costly: a gap in the certificate record cannot be fully healed after the fact.

Three further errors appear consistently in our practice:

Treating a fixed-term project extension as a new posting rather than a continuation, causing the 24-month clock to reset incorrectly
Failing to notify ZUS when the posting ends early, leaving an open certificate that creates contribution ambiguity
Omitting the receiving entity's full legal name and KRS number from the application, which triggers a ZUS request for clarification and adds weeks to processing

For workers who are non-EU nationals holding a work permit in Poland, an additional layer applies. The work permit specifies the employer and, in some cases, the worksite. Posting the worker to a different entity – even within Poland – may require a new or amended work permit before the A1 application can proceed. Employers who skip this step risk both a void A1 and a work permit violation. The Polish Border Guard (Straż Graniczna) and the National Labour Inspectorate (Państwowa Inspekcja Pracy, PIP) both have authority to inspect and fine for such violations.

For context on cross-border posting compliance across the EU, see our guide on global mobility and relocating employees to Poland from the Netherlands, which addresses comparable certificate requirements from the receiving-country perspective.

How do three business scenarios approach A1 compliance differently?

Understanding the procedure in the abstract is useful. Seeing how it applies to specific business models is more useful. The three scenarios below cover the configurations we encounter most often: a manufacturing group, an IT services provider, and a foreign investor's Polish subsidiary.

Manufacturing group with intra-group secondments. A German automotive supplier operates two Polish production facilities through separate Polish entities. When it moves a specialist engineer from the Kraków plant to the Warsaw plant for eight months, both entities are Polish. But the parent's HR system is German, and the engineer's employment contract is with the German parent. ZUS treats this as a posting under EU coordination rules. The employer must file US-36, attach the German parent's HR decision, and confirm the engineer has been in the Polish social security system for at least one month. Processing takes up to 25 business days. Cost: no ZUS fee, but internal HR preparation and legal review typically run PLN 2,000–4,000 per application.

IT services provider with multi-client deployments. A Polish IT consultancy employs developers who work simultaneously for two clients – one in Poland, one in Germany. These are multi-state workers, not posted workers. The applicable form is US-35, not US-36. The certificate confirms Polish legislation applies if the worker performs a substantial part of their activity in Poland (generally interpreted as more than 25% of working time). The consultancy must track working-time split by country and update ZUS if the split changes materially. Failure to report a change that shifts the worker into predominantly German activity precludes reliance on the Polish-law certificate – a gap that triggers German contribution claims retroactively.

Foreign investor's Polish subsidiary receiving posted workers. A Dutch holding company posts workers from its Amsterdam office to its Warsaw subsidiary for a product launch. The workers are Dutch nationals, covered by Dutch social security. The Warsaw subsidiary is the receiving entity. It does not apply for an A1 – that is the Dutch employer's obligation in the Netherlands. But the Warsaw subsidiary must verify that valid A1 certificates exist before the workers begin. If they do not, the subsidiary may be treated as the de facto employer in Poland, triggering Polish contribution liability. Our team secured interim relief from a contribution assessment exceeding EUR 300,000 for a foreign investor's subsidiary in Lower Silesia (spring 2025) where this verification step had been missed. For foreign investors structuring their Polish operations, see our overview of corporate and M&A in Poland.

What should employers prepare before filing an A1 application?

Preparation quality determines processing speed. ZUS's 25-business-day clock does not start until the application is complete. An incomplete file sits in a ZUS queue generating no certificate while the posting has already begun. The checklist below applies to standard posting applications; multi-state worker applications require additional working-time documentation.

Verify the employee has at least one month of continuous Polish social security contributions immediately before the posting start date
Obtain a current KRS extract for both the sending and receiving entities (dated within 3 months)
Confirm the work permit or EU Blue Card is valid for the receiving entity and worksite, if applicable
Prepare a posting agreement or addendum to the employment contract specifying the receiving entity, worksite, and period
Gather payroll records demonstrating substantial employer activity in Poland for the 12 months before posting

Employers operating across multiple EU member states should also review whether the posting falls under the Posted Workers Directive (Dyrektywa o delegowaniu pracowników) notification obligations in the receiving state. For Poland-to-Poland scenarios involving a foreign corporate chain, the notification may still be required in the foreign parent's jurisdiction. Employment compliance for companies operating across Central Europe – including posting notification rules in Slovakia – is addressed in our guide on employment law compliance for Slovakia companies in Poland.

Whistleblower protection rules in Poland (introduced under the Whistleblower Protection Act of 2024) also intersect with posting arrangements. Workers who report A1 non-compliance internally are protected from retaliation. Employers should ensure their internal reporting channels cover social security violations – the National Labour Inspectorate treats the absence of such channels as an independent compliance failure. A whistleblower Poland policy that excludes social security matters is a gap auditors will flag.

Finally, document retention matters. ZUS can audit A1 arrangements up to five years after the certificate period ends. Employers should retain the full application file, the issued certificate, and all supporting documents for at least six years from the end of the posting period.

Frequently asked questions

Q: Does an A1 certificate cost anything to obtain from ZUS?

A: ZUS charges no administrative fee for issuing an A1 certificate. The costs employers incur are indirect – internal HR preparation time, legal review of the application, and any corrections required if ZUS requests additional documents. For a single straightforward application, legal preparation typically takes two to four hours. Complex multi-state or intra-group posting structures may require more detailed analysis before the application is filed.

Q: Is it a common misconception that A1 certificates only apply when a worker physically crosses a border?

A: Yes – this is the most widespread misunderstanding in Polish HR practice. The certificate confirms which country's social security legislation applies, not where work is physically performed. When the employment relationship has an international dimension – a foreign contracting entity, a foreign parent company, or a cross-border payroll arrangement – the certificate may be required even if the worker never leaves Poland. The Polish Social Insurance Institution assesses the corporate structure of the arrangement, not the geography of the worksite.

Q: What happens if ZUS refuses to issue an A1 certificate?

A: ZUS refusal is not final. The employer may appeal the decision to the ZUS supervisory board (Zakład Ubezpieczeń Społecznych – organ odwoławczy) within 30 days of receiving the refusal. If the internal appeal fails, the employer can bring proceedings before the district labour and social insurance court (Sąd Rejonowy – Wydział Pracy i Ubezpieczeń Społecznych). Courts have overturned ZUS refusals where the employer demonstrated genuine substantial activity in Poland and a bona fide posting arrangement. Legal representation at both the administrative and judicial stages significantly improves outcomes.

Specific posting situations in your company require a tailored assessment. The absence of an A1 certificate where one is required can trigger retroactive contribution liability covering the full posting period – an outcome that cannot be undone once an audit begins.

If your company is posting workers within Poland under an international corporate structure, or if you are unsure whether your current arrangements require A1 certificates, contact info@kordeckipartners.com for an expert assessment of your specific situation.

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, global mobility, and social security coordination. We work with Polish entrepreneurs, foreign investors, and in-house legal teams. To discuss your situation, contact info@kordeckipartners.com.