First of all, speak or write to the person who is responsible for your payroll or salaries department, setting out why you think you have been paid incorrectly.
If you don't get a satisfactory answer to your complaint, speak to your manager and, if you have one, your union representative.
If you are not a member of a union, consider asking for the assistance of a colleague who you trust and who has a sound knowledge of the payment systems at your workplace.
If your complaint is not resolved through these informal means, you may have to raise a grievance using your organisation's formal grievance procedure.
If your employer fails to investigate your grievance or there remains a dispute, you might then consider whether to bring a claim to an employment tribunal (e.g. for unlawful deduction from wages). Before contacting the employment tribunal, you need to contact Acas to try and settle your claim under the Early Conciliation rules. It is not possible to make a claim in the employment tribunal until you have taken this first step. A tribunal claim needs to be made within the specified time limit, usually within three months of the action about which you are complaining.
If you are not the only person affected, consider getting together with your colleagues and organising a collective grievance.
For more information about bringing a claim, see our section on Enforcing your Rights.
If you think you have been paid too much, make sure you don't spend the additional amount until you have clarified with your employer why it has been paid to you and that you are definitely entitled to keep it. In general, your employer has the right to make deductions from your wages to recover sums paid to you by mistake, even if the mistake was their fault.