The employee failed to present full right to work documentation during a workplace audit. As a result they were dismissed by reason of illegality (one of the five permitted reasons for dismiss).
Initially an employment tribunal held that the dismissal was fair. However, the employment appeal tribunal held that properly conducted right to work checks simply excuse the employer from paying a penalty if it transpires that the employee did not have the right to work. Not undertaking the checks is not an offence. The employer's erroneous belief to the contrary could not amount to illegality, although, it could amount to some other substantial reason for dismissal (which should have been used as the correct reason for dismissal).
Employers should be cautious before deciding not to insist on an employee providing right to work documentation, because of the potential penalties if it is later discovered that the employee is working illegally.