If you’re from the EU/EEA or Switzerland
If you’re from the European Union (EU), European Economic Area (EU plus Iceland, Lichtenstein and Norway) or Switzerland, as long as you have a valid passport or ID card, you currently don’t need a visa to come to the UK or a work permit to take on employment in the UK, although this changed after March 2019 when the UK is due to begin the process of leaving the EU.
If you’re not from the EU/EEA or Switzerland but you’re living with a partner or other family member who is, then you can apply for residence card which shows employers that you’re allowed to work in the UK.
f you’re from outside EU/EEA or Switzerland
You’ll probably need a visa to come to the UK; apply at the British embassy or consulate in your home country. If you want to work in the UK you will have to have a work permit. Your employer in the UK has to apply for a work permit on your behalf relating to a specific workplace.
There are different types of visa to come and work in the UK, depending on your qualifications, area of work, your skills, talents and age; each visa has different conditions and may require you to pass a points-based assessment. For example, you may have to be a graduate, have been already offered a job in the UK which cannot be filled by someone else from the EU/EEA/Switzerland, have a licenced sponsor (see a list of registered sponsors here), or prove that you have a good knowledge of English by taking an exam or having a language qualification.
Students can work as employees, although not as self-employed, for up to 20 hours a week in term time (more if the work is part of the course) and outside term time as long as the position is not full-time or permanent. PhD students can stay in the UK and look and start work in the UK for a year after their studies end.