Grievance Procedures: What UK Employers Must Do

Employees have the right to raise a formal grievance if they have a complaint about their work, working conditions, or the behaviour of a colleague or manager. How you handle that grievance — not just the outcome — determines your exposure if the dispute escalates to a tribunal.

The ACAS Code of Practice requires: a written grievance from the employee (or acknowledgement that one was raised verbally and recorded); an investigation; a formal meeting where the employee can set out their complaint and be accompanied; a written decision; and a right of appeal. If you dismiss an employee after they have raised a grievance, and the grievance was connected to the dismissal, that is automatically unfair dismissal.

HR managers often treat grievances as a problem to close quickly. A better frame is that they are an early warning system. A grievance tells you something is wrong — with a relationship, a process, or a management behaviour. Mellow logs grievance cases with the same rigour as disciplinaries. The outcome letter, the appeal decision, and the underlying investigation notes are all stored. If the same manager appears in multiple grievances over time, that pattern is visible.