The UK government has an easy to use tool for checking someone’s right to work, available at https://www.gov.uk/legal-right-to-work-in-the-uk. As rules may change dependent on rulings either from the UK government or the European Union, this provides the most up-to-date source of information.
You can be prosecuted for employing illegal workers, including students with expired visas, students working more hours than they’re allowed to and people on a visitor’s visas.
At the time of preparing this guide the fines for employing people illegally are severe, with penalties for those committing the offence being up to £10,000 per worker.
However, the UK government is strengthening its crackdown on the employment of illegal workers. In the forthcoming Immigration Bill, to be introduced in Autumn 2016, there will be new measures leading to those caught working illegally in England and Wales to be sentenced to up to six months in jail.
For an employer, claiming that one did not know that an employee was an illegal worker will not be an acceptable legal defence; an employer will have to show that they have carried out proper checks prior to offering a job. The maximum sentence for an employer found guilty will be raised from two to five years, in addition to the fines already available.
Details of existing penalties for employers employing illegal workers may be found at https://www.gov.uk/government/collections/employers-illegal-working-penalties.