The Gov.UK website has recently published a list of employers by region who have not complied with illegal working legislation and have been subject to a civil penalty.
The penalties have been awarded because the employer has not paid, or started to make payments towards the penalties after exhausting appeal procedures or has been served with second or subsequent penalties.
The list consists mainly of local restaurants, takeaways and car washes. One employer, a restaurant, in the London and South East England area has been awarded a penalty of £100,000.
https://www.gov.uk/government/collections/employers-illegal-working-penalties
There is a handy online tool on the Gov website which enables employers to carry out a quick check.
Employers should carry out any checks to ensure that an employee or worker is legally entitled to work in the UK are carried out prior to the start of employment.
For example, asking a new employee to present a copy of their Passport on their first day of employment is not an acceptable defence against illegal working.
Further guidance can be found here.