Posting Workers Into Bulgaria: A1 Certificates and Employer Registration Explained

When an employer sends a worker into Bulgaria for a defined assignment, whether a construction project, an installation, or a client secondment, the arrangement is a posting rather than a local hire, and it triggers a distinct set of compliance obligations under Bulgarian law. For employers in Romania, Serbia, and elsewhere who use Bulgaria as a nearshoring or project destination, understanding where posting obligations begin and end, and how they differ from the requirements of a standard local employment relationship, is essential before the first worker arrives on site.

Registering as a foreign employer with Bulgaria's National Revenue Agency

Any foreign employer that concludes an employment relationship with a person whose place of work is in Bulgaria generally needs to register with Bulgaria's National Revenue Agency, the NRA, before that work begins. This applies whether the employer is posting an existing employee temporarily or establishing an ongoing local employment relationship. Registration typically requires a certificate of good standing from the employer's home country, identification for the company's legal representative, and the employer's home-country tax registration documentation, with all foreign-language documents needing apostille certification and sworn translation into Bulgarian before submission. Processing for a complete registration file is generally measured in a small number of business days once the NRA has everything it needs, though employers should build in time for the apostille and translation steps that typically precede submission.

Once registered, the employer takes on ongoing obligations distinct from the one-time registration step itself:

• Registering each posted or locally employed worker for social and health insurance coverage
• Submitting the underlying employment contract, or the posting documentation, to the NRA before work commences
• Filing monthly contribution and tax declarations for the duration of the employment or posting
• Maintaining payroll and employment records in line with Bulgarian labour law recordkeeping requirements

A1 certificates: keeping social security in the sending country

For postings from another EU member state, the A1 certificate is the mechanism that keeps a worker covered by their home country's social security system rather than Bulgaria's, for the duration of the assignment. This follows the EU's social security coordination framework, Regulation 883/2004, under which an employee is covered by the social security system of only one member state at a time. A Romanian or Bulgarian-neighbouring EU employer posting a worker into Bulgaria should secure the A1 certificate from the relevant home-country social security authority before the assignment begins, and the worker should be able to produce it if asked during the posting.

Where no A1 certificate has been issued, or where the posting does not meet the conditions for A1 coverage to apply, the default position under EU coordination rules is that the worker becomes subject to Bulgarian registration and contribution requirements instead, meaning the employer may need to register the posted worker for Bulgarian social and health insurance in the same way as a locally employed worker. This default makes the A1 certificate not just a formality but a determinant of which country's contribution regime actually applies to a given posting.

For postings from outside the EU, for example from Serbia, the A1 mechanism under Regulation 883/2004 does not apply in the same way, since that framework governs coordination among EU and EEA states. Employers posting workers into Bulgaria from a non-EU country should confirm separately whether a bilateral social security agreement between Bulgaria and the sending country addresses social security treatment during the posting, since the answer determines whether Bulgarian registration is required from the outset.

How this differs from the single permit route

Posting compliance under the NRA registration and A1 framework is a distinct track from Bulgaria's single permit process, which governs non-EU nationals seeking ongoing employment authorisation in Bulgaria through the standard work-and-residence permit route. A posting is, by definition, temporary and tied to an assignment with an end date, with the worker typically remaining employed by the sending employer throughout. An employer that is actually establishing a long-term Bulgarian role, rather than a defined-duration assignment, should assess whether the posting framework is the right fit at all, since treating what is functionally a permanent transfer as a posting can create its own compliance exposure if challenged.

Practical risks employers should plan around

• Starting work in Bulgaria before NRA registration is complete, which exposes the employer to the registration requirement being enforced retroactively alongside potential penalties
• Relying on an A1 certificate that does not accurately reflect the actual terms of the posting, since EU case law has addressed situations where an A1 certificate issued on an incorrect factual basis does not fully protect the employer from host-country enforcement
• Assuming a non-EU sending country's workers are automatically covered by a social security agreement with Bulgaria without first confirming that agreement exists and what it actually covers
• Treating NRA registration as a one-time task rather than an ongoing filing obligation, since monthly contribution and tax declarations continue for as long as the posting or employment relationship runs

How Nestlers Group supports employers posting into Bulgaria

Nestlers Group's Tax Services team manages NRA registration for employers posting or employing staff in Bulgaria, including coordinating the apostille and certified translation of home-country corporate documents that registration requires. Where a posting originates from an EU member state, our Tax Services team also handles A1 certificate applications and verifies that the certificate accurately reflects the posting's actual terms before it is relied upon. For postings from outside the EU, our Consultancy advisors confirm whether a bilateral social security agreement applies and what Bulgarian registration obligations follow if it does not, so employers are not caught relying on an assumption that does not hold for their specific sending country.

Sources: payrollbg.bg, registration requirements for foreign employers in Bulgaria; Regulation (EC) No 883/2004 on the coordination of social security systems; Bulgarian Ministry of Labour and Social Policy, Labour Migration and Labour Mobility Act; CMS Law, Posting of Workers Directive 2014/67/EU transposed into Bulgarian legislation.