If the employer has overpaid an employee by mistake then the employer has the right to reclaim that money back.
However, employees and workers are protected, under section 13 of the Employment Rights Act 1996, from any unlawful deductions from their wages. The exception to this is section 14 of the Act which provides for the case of an overpayment, allowing employers to make a deduction and correct the error. Furthermore, an express provision in many employment contracts allows corrections to be made in case of payroll errors.