Where an employer has accidentally overpaid an employee, is the employer obliged to obtain the employee's written consent before making deductions from their salary to reclaim the overpaid amount?

No, it is not necessary for an employee to consent to deductions from their wages made to recover an accidental overpayment, but it is preferable for the employer to obtain the employee's consent, to avoid any future dispute.

If the employer makes deductions without the employee's consent, the employee cannot bring a claim in the employment tribunal, because the provisions of the Employment Rights Act 1996 that protect employees from unlawful deductions from wages do not apply to the recovery of overpayments. However, the employee could bring a claim in the civil courts, under common law principles, arguing that the employer was not entitled to recover the money. Obtaining the employee's consent before making the deduction will protect the employer from such a claim.