In an increasingly globalized business environment, posting employees within the European Union (EU) is becoming a common practice—whether for short-term projects, training, or the provision of services. However, employers often underestimate the administrative and legal aspects related to this process. One of the key documents when posting workers in the context of the provision of services is the A1 certificate, which proves which national social security legislation applies to the posted employee.
1. What is the A1 certificate and when is it required?
According to Regulation (EC) No 883/2004 and Regulation (EC) No 987/2009, every worker in the EU is subject to social security in only one Member State. In Bulgaria, the A1 certificate is issued by the National Revenue Agency (NRA) and confirms that the employee remains insured under Bulgarian legislation, even though they are temporarily working in another Member State.
Such a document is required for:
Posting of workers in the context of the provision of services – when a Bulgarian company sends its employees to work temporarily in another Member State under a contract with a local client;
Intra-corporate transfers between branches or companies of the same group established in different Member States;
Temporary employment agencies posting workers to a user enterprise in the territory of another Member State.
The posting period usually must not exceed 24 months. Upon the expiration of the posting period, a new posting period for the same employee, the same enterprise, and the same Member State can only be authorized after at least two months have elapsed since the expiration date of the previous posting period.
2. Key requirements for issuing an A1 certificate
For the employer to post an employee while keeping the Bulgarian social security legislation applicable, the following conditions must be met:
The employer normally carries out a significant part of its activities in Bulgaria (e.g., over 25% of turnover, staff, or contracts);
The employee has a valid employment relationship with the Bulgarian employer throughout the entire posting period;
The posting is of a predetermined duration, and upon its completion, the employee returns to work in Bulgaria;
The activity in the host country does not constitute a replacement of another posted employee whose term has already expired.
3. When is the employer not required to initiate the A1 certificate procedure?
Not all cases of sending an employee abroad require the issuance of an A1 certificate. Such a procedure is not required when:
The employee is hired directly by a local employer in the host country and is subject to social security under its legislation;
The work abroad does not constitute posting within the meaning of Regulation (EC) No 883/2004 but is part of an employment contract concluded directly with a foreign company;
The work is performed outside the EU – in this case, bilateral social security agreements apply, if any;
The employee permanently resides and works in another country, and Bulgaria is no longer their “center of vital interests” within the meaning of social security;
The employee is sent for a short term for training, a conference, or a short visit that does not have the nature of a provision of services and involves no actual labor (according to NRA practice, such cases are treated as business trips rather than posting).
4. What are the employer’s obligations when posting workers?
In addition to securing the A1 certificate, the employer must also comply with the following requirements:
Concluding an annex/agreement to the employment contract regarding the posting;
Providing travel expenses at the employer’s expense;
Providing working conditions and remuneration no less favorable than those in the host country;
Providing written notification regarding the working conditions in the host country;
If necessary – submitting a prior notification to the host country.
5. Practical advice for employers
Plan ahead – the procedure for issuing an A1 certificate usually takes 30 calendar days.
Check the client’s status – if you are sending employees to a local company, verify the registration requirements in the host country.
Keep records – retain all posting orders, agreements, and evidence of actual business activity.
Samokovliyska Law Firm assists employers with:
Issuance of A1 certificates and other documents related to cross-border employment;
Preparation of agreements, posting orders, and employment contracts;
Legal analysis of the applicable legislation;
Communication with institutions.
Our goal is to ensure that every posting is legal, secure, and efficient, allowing the employer to focus on the business rather than administrative barriers.
