A complaint has been made. Now what?

It might come as a formal written complaint. It might come as a tearful conversation in your office. It might come as a call from a lawyer. However it arrives, the moment an allegation of misconduct, bullying, harassment, or other serious workplace behaviour hits your desk, the clock starts ticking.

How you handle the first 48 hours — and the investigation that follows — will determine whether the matter is resolved properly or whether it turns into a Fair Work claim, a workers' compensation claim, a regulatory complaint, or worse.

After two decades of advising employers through workplace investigations, here's what you need to know.

When do you need a formal investigation?

Not every issue requires a full investigation. A minor interpersonal disagreement might be resolved through a facilitated conversation. But certain matters demand a formal, documented process. These include allegations of bullying or harassment, sexual harassment, discrimination, serious misconduct (theft, fraud, safety breaches), psychosocial safety concerns, and whistleblower disclosures.

If you're unsure whether the situation warrants a formal investigation, err on the side of doing one. The risk of under-responding is almost always greater than the risk of over-responding.

The five principles of a fair investigation

The Fair Work Commission and courts will assess whether your investigation was procedurally fair. That means it needs to meet five basic principles.

Timeliness. Investigations should be commenced as soon as reasonably practicable after the complaint is received. Unnecessary delays undermine credibility and can cause further harm to the people involved.

Impartiality. The investigator must be — and must be seen to be — independent and unbiased. If the complaint involves a senior leader, a close colleague of the decision-maker, or the decision-maker themselves, an external investigator should be engaged.

Procedural fairness. The respondent (the person the complaint is about) must be told the substance of the allegations against them and given a genuine opportunity to respond before any findings are made. This is non-negotiable.

Confidentiality. Information should be shared only on a need-to-know basis. Both the complainant and respondent should be reminded of their confidentiality obligations. Breaches of confidentiality can compromise the investigation and expose the employer to further claims.

Evidence-based findings. Findings must be based on the evidence gathered — witness statements, documents, records — not assumptions, gut feelings, or prior opinions about the people involved.

Common mistakes employers make

Trying to handle it informally when it's serious. Some matters cannot be resolved with a quiet chat. If the allegation involves harassment, discrimination, or serious misconduct, a formal process is not optional — it's a legal obligation under your duty of care.

Investigating without a plan. Before you interview anyone, you need to be clear on the scope of the investigation, the allegations to be tested, the witnesses to be interviewed, the documents to be reviewed, and the timeline. Going in without a plan leads to missed evidence and procedural gaps.

Failing to support the parties involved. Both the complainant and the respondent are likely to be under significant stress. Employers should ensure both parties have access to EAP, are informed of the process and timeline, and are not subjected to victimisation or adverse action during the investigation.

Not separating the investigation from the decision. The person who investigates should not be the same person who makes the disciplinary decision. Separation of roles is a key element of procedural fairness.

Taking too long. Investigations that drag on for months erode trust, increase the risk of mental health impacts, and often result in key witnesses becoming less reliable. Aim to complete investigations within 2–4 weeks where possible.

When to use an external investigator

You should consider engaging an external investigator when the complaint involves senior management or directors, the matter is complex or high-risk, there is a potential conflict of interest, the organisation lacks internal investigation capability, or the matter may result in litigation or regulatory scrutiny.

An external investigator brings independence, expertise, and credibility — all of which strengthen the defensibility of the outcome.

What happens after the investigation?

Once the investigation is complete, the investigator provides a report with findings. The employer then decides on the appropriate outcome — which may range from no action, to training, to a formal warning, to termination. The outcome must be proportionate to the findings and consistent with how similar matters have been handled previously.

Both parties should be informed of the outcome in writing. The complainant doesn't need to know the specific disciplinary action taken against the respondent, but they should be told that the matter has been investigated and appropriate action taken.

The bottom line

Workplace investigations are not something to wing. A poorly handled investigation can turn a manageable workplace issue into a six-figure legal problem — and cause lasting damage to your people and your culture.

If you're facing a workplace complaint and aren't sure how to handle it, or if you need an independent investigator, get in touch with our team. We conduct workplace investigations across Australia for employers of all sizes.

Industrial HR provides practical, precise HR and industrial relations support for Australian businesses. For more information, visit industrialhr.com.au.