A1-Bescheinigung for foreign subcontractors: what general contractors must check

What is the A1-Bescheinigung?

Under EU Regulation 883/2004, the A1 certificate (in German: A1-Bescheinigung) documents which country's social security law applies to an employee or self-employed person working temporarily in another member state. With a valid A1, the workers of your Polish subcontractor stay insured in the Polish system — without one, German social security law applies by default from day one, with all the contribution consequences that entails. For you as a general contractor (Generalunternehmer, GU), the takeaway is simple: the A1 belongs in the file for every posted worker before their first day on site.

Who needs an A1 certificate?

• Every posted worker employed by an EU/EEA subcontractor — per person, not per company
• Self-employed contractors working temporarily in Germany — the one-man subcontractor from the Czech Republic needs his own A1
• On longer projects: watch the validity period — the A1 is issued for a limited time and must be extended when the project runs longer

Your role as GC during a customs inspection

When the Finanzkontrolle Schwarzarbeit (FKS — the German customs unit that polices undeclared work) inspects your site, the A1 certificates for every foreign worker must be available for inspection. Legally, the posting employer is responsible — in practice, the inspection hits you: site shutdown, interviews, follow-up audits. A general contractor who has a current A1 on file for each posted worker ends such inspections in minutes instead of days.

Typical problems in practice

• A1 "being processed": Retroactive issuance is possible, but during an inspection only the moment of the check counts. Require the A1 before the first day of work.
• Crew changes: The subcontractor swaps people in and out — and the new ones have no A1. Tie your site access list to the A1 list.
• Expired certificates after a project extension: the classic blind spot once a job passes the 12-month mark.

How to organize your A1 management

1. Contract clause: an A1 for every worker deployed, delivered before work starts; extensions to be submitted without being asked
2. Per-person filing: A1 + ID copy + residence permit (where applicable) for each worker
3. Track validity: reminder 30 days before expiry — sent directly to the subcontractor, ideally in their own language. Our guide to deadline management for certificates (in German) shows how to set up such a system.
4. Cross-check against the actual workforce on site (access lists, site diary)

The A1 is just one of many mandatory documents per subcontractor — for everything else that belongs in every subcontractor file, see the subcontractor document checklist.