The European Commission has created a page to self assess which immigration category different workers fit into, providing access to key information on residency and immigration requirements. Here's an overview.
The European Commission has published an interactive page to help people who work or are seeking work in the European Union to access the necessary requirements and eligibility criteria for their particular situation.
Here is a summary of the six different categories listed.
Highly qualified workers and the EU Blue Card
These are individuals who have a work contract in the EU as well as proof of a higher professional qualification or equivalent experience. They must work as paid employees.
An EU Blue Card gives highly-qualified workers from outside the EU the right to live and work in an EU country, provided they have higher professional qualifications, such as a university degree, and an employment contract or a binding job offer with a relatively high salary in the EU country where the job is based. For example, the annual salary threshold for Germany and France was €53,600 and €53,836 respectively, according to information by the EC in July 2021.
Intra corporate transferees (ICT)
This category relates to individuals from third countries with a work contract in a company established outside of the EU who are temporarily transferred to the branch/es of that company in one or several EU countries (with the exception of UK, Denmark and Ireland).
The spouse/partner of intra corporate transferees may be authorized to stay and work in the EU during the period of their transfer. However, it is helpful to check the page related to ICT of each specific member state (you can find this by searching for "Intra corporate transferees" + the country name) and the provisions of the corresponding EU directive, the Directive 2014/66/EU, which you can find here.
This section concerns individuals who wish to carry out research in an EU country for more than three months and who have a signed hosting agreement with an authorized research organization.
Researchers will generally be eligible for a residence permit valid for at least one year (or where the project lasts for less than a year -- residence permit will cover the duration of the project). This will be renewable for as long they continue to meet the necessary conditions.
A visa may be required, depending on the nationality of the researcher and the rules in the EU country where they plan to do their research. For information on the visa requirements, select the relevant country on this map.
In some EU countries researchers will be allowed to teach for a certain number of hours or days per week. In other countries this will not be the case, therefore it is important to check the country specific information. Generally, it will be possible for researchers to bring their family for the duration of their stay -- refer to the above map for more details.
A seasonal worker is an individual from a non-EU country with a work contract for seasonal employment with a company established in an EU country (with the exception of Denmark and Ireland). They must also present a valid passport or another travel document, health insurance, proof that of accommodation during their stay.
Potential seasonal workers must submit an application for a visa, or work permit or a residence permit (depending on the EU country and the duration of their stay) to the competent national authorities of the EU country where they will work.
The application must be submitted when the individual is still outside of the EU. In some cases the employer must submit that application and usually the company or individual will also need to pay a fee for the processing of the application.
The seasonal work visa or permit will be valid for the duration of the seasonal work contract and it is important to note that this visa or permit only allows the worker to work and live in the EU country that issued it. In addition, as a seasonal worker, workers are not permitted to bring their family to live with them in the EU country where they will work.
This refers to individuals who has been admitted to a higher education instituted to follow a full-time course of studies in an EU country and full the necessary conditions.
Students may work on a part-time basis. Each EU country can set its own limit on the maximum amount of hours they can work but must allow a minimum amount of ten hours per week. In some cases the individual or the employer may have to inform the relevant national authorities that they are working.
In some countries, students may only start work after having been resident for one year -- check the rules of relevant EU state. If a person has been admitted as a student in one EU country, they may go on to study in another EU country if they are doing so to continue their course or to study a related subject.
However, if an individual overstays the validity period of the student residence permit, they will be in an irregular situation and may be required to leave the country. This also applies to all the other categories listed.
Unpaid Trainees, Exchange School Pupils and Volunteers
These include individuals with a signed training agreement for unpaid work or proof of being part of an organized program, and meet the necessary age requirements. To be eligible they must also provide proof of sufficient financial resources and health care coverage to support themselves. Depending on the rules in the relevant EU country, pupils, trainees or volunteers may also be required to take part in a basic introduction to the country’s language, history and political and social structures.
Residency permits relating to unpaid trainees, exchange pupils or volunteers residency will generally last for up to one year or for the duration of the programme if this is a shorter period.