It is generally not illegal for an employee to be off sick from one job and receive sick pay, whilst continuing to work in a second job for another employer. Many employers automatically and, incorrectly, refer to this as the employee 'defrauding' the company and even take disciplinary action, up to and including dismissal.
However, the legal position is that as long as the employee is genuinely certified unfit to work and this affects their ability to carry out the specific job from which they are signed off, they are able to be off sick from it. In the meantime if they are capable of performing another job, which is not affected by the reasons for being signed off sick, they can do so. Such a job should not be undertaken during the hours of the job from which they are signed off, as the employee would then be paid twice for the same hours, which is not allowed.
For example, a worker has two jobs – a daytime job in an office and an evening job in a shop. They are signed off sick from the daytime job due to workplace stress as a result of heavy workload or bullying by colleagues. The stress prevents them from working in that specific job as the stressors are directly connected to it. It does not prevent them from continuing to work in the evening job, which is less stressful and is not affected by the reasons for being off sick.
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