Line Managers Guide to Workplace Investigations

This guide has been created to help line managers conduct workplace investigations fairly, consistently, and legally. It follows the key principles of the ACAS Code of Practice and is tailored to the needs of smaller organisations, where the line manager often conducts investigations that may take place either face-to-face or via Teams.

Why This Guide Matters

Workplace investigations are crucial for addressing concerns, complaints, and allegations. A well-run investigation:

• • • Finds the facts — it establishes what happened, when, and who was involved.
    • Protects fairness — it ensures everyone is treated consistently and without bias.
    • Builds trust — staff are more likely to have confidence in the outcome when the process is transparent and even-handed.
    • Reduces legal risk — tribunals and external bodies expect employers to follow a fair process; failure to do so can lead to reputational damage, financial loss, and findings of unfair dismissal.
    • Supports decision-making — clear, factual evidence allows the organisation tomake sound, proportionate decisions about next steps.
    • Following the steps in this guide will help you:
      1. Stay compliant with the ACAS Code of Practice and good-practice guidance.
      2. Act promptly and proportionately, avoiding unnecessary delays.
      3. Keep the process impartial by focusing on facts rather than assumptions.
      4. Maintain confidentiality and handle personal data appropriately.
      5. Document the process clearly so that evidence can support decisions if ever questioned.

      This guidance ensures that every investigation, no matter how small the issue may seem, is conducted with professionalism and consistency. By following it, you protect both the organisation and the individuals involved while helping to create a workplace culture where issues are addressed fairly and effectively.