Since July 2016, under section 21 of the Immigration, Asylum and Nationality Act 2006 there have been 3 people prosecuted.
Immigration Enforcement will review investigations into employers on a case by case basis to see whether a civil penalty is a more appropriate course of action rather than a criminal prosecution. Where there are no aggravating factors, it is more likely that civil penalty action will be undertaken to enforce compliance.
Data on the number of penalties issued under section 15 of the Immigration, Asylum and Nationality Act 2006, and the total value of those penalties are published on gov.uk. A total of 5,856 civil penalties were issued between July 2016 and June 2019, with a total value of £100.1m.