How to Run a Fair Disciplinary Investigation (before you hold a hearing)
Most disciplinary cases are won or lost before anyone sits down in a disciplinary hearing. They are won or lost in the disciplinary investigation stage. Get that part right and the rest of the process is generally a lot easier. Get it wrong and even a fair disciplinary outcome can be picked apart later.
We see this a lot at Keeping HR Simple. A manager spots a problem, feels sure of what happened, and jumps straight to a disciplinary hearing. Then further down the line an Employments Tribunal asks one simple question. Did a fair investigation take place first?
If the answer is no, the dismissal can be ruled unfair even when the employee was responsible for the action/s they were accused of. That feels harsh to a lot of business owners, but it is how the law works. A fair process matters as much as the facts.
So here is how to run an investigation that stands up to scrutiny.
When Do You Actually Need a Disciplinary Investigation?
Not every issue needs a formal disciplinary investigation. A one-off lateness or a minor slip can usually be sorted with a quiet word and a note on file. But once you are thinking about formal action, you have to gather the facts first.
The test from the Acas Code of Practice is reasonableness. A reasonable investigation should be carried out so you can form a genuine and honest belief, on reasonable grounds, that misconduct took place. You do not have to prove it beyond all doubt. You do have to show that you investigated.
The scale of the investigation should match the seriousness of the allegation. A missed deadline needs far less digging than an accusation of theft, dishonesty or gross misconduct. And remember that suspension is sometimes an option, but it is not a punishment and should never be automatic. If you do suspend, keep the period of suspension as short as possible and tell the employee it is a suspension pending investigation. Suspension should be on full pay.
Keep The Investigator And The Decision Maker Roles Separate
This is the mistake we see most often. In a small business the same person often does everything. They notice the problem, investigate it, run the hearing and decide the outcome. And that feels efficient. But it can quietly undermine fairness.
Wherever possible, the person who investigates should not be the person who chairs the disciplinary hearing or decides the sanction. The reason is simple. Someone who has gathered all the evidence has usually formed a view by the https://keepinghrsimple.co.uk/how-to-run-a-fair-disciplinary-investigation/end of it. They are no longer neutral, even if they think they are. A fresh pair of eyes and ears at the hearing keeps the process fair and impartial as possible.
In very small teams that split is not always possible. If you genuinely cannot separate the roles, write down why, stay alert to your own bias, and think about bringing in outside support so the process is seen to be even handed. We do this for clients regularly, and it often saves a lot of grief later.
How Long Should a Disciplinary Investigation Take?
There is no fixed rule, but the honest answer is as long as it needs and no longer. Acas guidance is clear that an investigation should be done as quickly as possible while still being thorough and fair. A simple case might take a day to gather what you need. A more complicated one, with several people to speak to, can take a number of weeks.
Set a sensible timescale at the start and tell the employee what it is. Long silences are where trust breaks down. We see a manager go quiet for a month during an investigation while an employee sits at home worrying, and that on its own can sour the whole process. If you find you need more time, that is fine but explain the delay to everyone involved and note it in your report. A short, well-run investigation usually beats a slow one that drifts.
Investigation Meetings Are Not The Disciplinary Hearing
People mix these two up all the time, so it is worth being clear about the difference.
An investigation meeting is fact finding. You are asking what happened, when, who was there and what was said. It is a conversation, not a trial. The employee has no statutory right to be accompanied at this stage, although letting them bring a colleague can build goodwill and is rarely a bad idea. No decision about warnings or dismissal should be made at this time.
The hearing may come later. That is where the allegations are formally put to the employee, they get a proper chance to respond, and an outcome is decided. The right to be accompanied does apply at that point. Our guide to chairing a disciplinary hearing walks through that stage in full detail, so read the two together.
Keeping the line clear in your own mind stops the investigation drifting into an accidental hearing.
Gathering Evidence And Witness Statements Fairly
Be thorough, and be neutral. The point of an investigation is not to build a case against someone. It is to find out what actually happened, including anything that helps the employee. That last bit gets forgotten a lot. Follow the evidence, don’t loom for proof of what you think happened.
Collect the documents that matter. Emails, messages, rotas, CCTV, system logs, attendance records, phone records, whatever is relevant to the allegation. Date everything and store it securely. Stick to the specific issue in front of you and resist the urge to trawl through someone’s whole history looking for other problems.
Be mindful of the law while you do it. Data protection rules still apply, so only gather what is relevant and proportionate, and respect the employee’s privacy. If you are relying on CCTV, vehicle trackers, call logs or computer records, your staff should already have been told that this monitoring exists and could be used in a case like this. Keep a written note of how and why you obtained each piece of evidence. If anyone questions later whether you overstepped, that record is what protects you. The Information Commissioner’s Office has clear guidance if you are not sure where the line sits.
For witness statements, speak to people while memories are fresh. Ask open questions (who, what, where, why, when and how) rather than closed ones (yes/no answers), write up what they say, and get them to read it back and sign it. Some witnesses will worry about reprisals, so handle confidentiality with care and reassure them where you can. A signed and dated statement is worth far more than a vague recollection dragged up six months later.
Searching Desks, Lockers And Personal Items
This one can catch employers out, so tread carefully. You should only search someone’s desk, locker, bag or vehicle in exceptional circumstances where it is clearly justified. Even when the contract allows it, you will usually still need the worker’s consent for the search to be lawful.
If you do need to search, invite the employee to be there. If they cannot attend, have a manager present as a witness, and record every request and every refusal in writing. Do not jump to conclusions if someone says no. A refusal is not proof of guilt, and the person may have a perfectly good reason for it, so that should be taken into consideration rather than assuming the worst.
If you think a criminal offence may have happened, such as theft, you can involve the police, who have far wider powers to search than you do. You might then put your own disciplinary investigation on hold until things are resolved, or carry on carefully so you do not affect any criminal case. Organisations that work with children or vulnerable adults may also have safeguarding duties to report certain matters, so factor those in early.
Writing The Disciplinary Investigation Report
Once you have the facts, write them up. The report does not need to be long but it does need to be clear.
A good disciplinary investigation report sets out the allegation, what you did to look into it, the evidence you found, and a recommendation on whether there is a case to answer. Attach the evidence and the statements. Stick to facts and leave opinions out of it. If you found things that point both ways, say so. A balanced report reads as fair, and a fair report is much harder to attack.
This document becomes the backbone of the pack you send to the employee ahead of any hearing, so it has to be written to a high standard.
Deciding Whether There Is A Case To Answer
This is the moment the whole investigation revolves around. Before you decide, weigh the evidence properly. Look at the parts that support the allegation and the parts that do not. Ask how credible and reliable each piece of evidence really is, and whether anything new has turned up that points the other way or means you should dig a little further. Your job here is to establish the facts, not to confirm a hunch you walked in with.
Then you look at what you have found and ask one honest question. Is there enough here for a reasonable employer to take this forward to a formal hearing?
Sometimes the answer is no. Maybe the evidence does not stack up, or there was a genuine misunderstanding. If so, close it down, tell the employee in writing that no further action is being taken, and move on. That is not a failure. It is the system working as it should. Identify any key learning points and implement those as soon as possible (e.g a process was not in place or was not clearly explained).
If there is a case to answer, you move forward with a clear, evidenced pack and a credible investigation process.
Why A Good Investigation Protects You At The Disciplinary Hearing
Here is a point worth thinking about. From January 2027 the qualifying period for unfair dismissal in the UK drops from two years to six months, and the cap on compensation is being removed. In simple terms, more of your employees will be able to bring a claim, sooner, and the financial stakes go up. A considered, well documented investigation is the cheapest insurance you can buy against that.
Making sure that your invitation to the disciplinary hearing is correct, is as crucial as the investigation; check out our guide to inviting employees to a disciplinary hearing for more information and a free template you can use.
If you would like a second pair of eyes on a live case, or you want your managers trained to handle this properly, the friendly team at Keeping HR Simple is here to help.
