ACCIDENT INVESTIGATION
Accident Investigation Report: Structure and Template
How a chartered investigator structures an accident investigation report so it holds up with the HSA, the HSE, your insurer and your board. Ten sections, what goes in each, and the drafting mistakes inspectors pick up first. Need yours checked against your legal duties? Talk to a chartered consultant.
Form or report
What an Accident Investigation Report Has to Prove
An accident investigation report is the written record of an investigation: what happened, why it happened, and what your organisation is changing so it does not happen again. Most of what ranks for the term is a blank form. A form captures the event, while a report has to prove a causal chain and show the fix that answers it.
The method behind the report, from freezing the scene to root cause, sits on our accident investigation service page, so this guide stays on the document itself. HSE guidance gives the report its spine in four parts.
1. Information Gathered
What happened, when, where and who was involved, set out as fact and referenced to the evidence collected on site.
2. Analysis
Why it happened, worked down from the immediate cause through the underlying causes to the root cause in how work is planned and managed.
3. Risk Control Measures
Which controls failed or were missing, and what replaces them, chosen from the top of the hierarchy of control downwards.
4. Action Plan
Who does what, by when, and how completion is verified. This is the part inspectors return to on the revisit.
The template outline
The Ten Sections of a Defensible Report
This is the outline our chartered investigators write to. Use it as a checklist of sections and questions rather than a form to copy. Every report we issue is written for the event and the site, never pulled from a template library.
The outline expands the four steps in HSE guidance HSG245 into ten sections. Each section ends with the question it has to answer. If a draft section cannot answer its question, the gap sits in the investigation rather than in the writing.
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Title page and document control
Report reference, date and time of the event, site and location, version number, status (draft or final), author, reviewer and the distribution list. Every later revision updates this page rather than creating a second report.
The question it answers Which version is the record, and who has seen it?
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Executive summary
One page. What happened, the root cause in a sentence, the actions that matter most and who owns them. We write it last, once the findings are settled, so it never promises more than the analysis supports.
The question it answers What does a director need to know in two minutes?
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Scope and terms of reference
Who commissioned the investigation, the level it was graded at under HSG245 (minimal, low, medium or high), what is in and out of scope, the target dates, and the investigator’s independence from the work being investigated.
The question it answers What was this investigation asked to answer, and by whom?
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Description of the event
A factual account of the task, the people involved, the plant and equipment, the conditions, the injury or damage and the emergency response. It carries no conclusions and no adjectives that judge anyone.
The question it answers Would everyone involved agree this is what happened?
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Sequence of events
A timeline from the last known normal state, through the event, to the end of the emergency response. Each entry is referenced to evidence, and gaps are marked as gaps instead of being filled with assumption.
The question it answers Does the sequence hold together without guesswork?
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Evidence register
Every photograph, measurement, witness account, CCTV clip and document (RAMS, method statement, permit to work, training records, maintenance history) listed with a reference, its source, the date collected and where the original is held.
The question it answers Can every finding be traced to something on the file?
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Analysis and findings
Immediate, underlying and root causes, the method used to reach them (5 Whys, fishbone or bowtie), and a cross-reference from each finding to the evidence register. Fact, finding and professional opinion are labelled so you can see which is which.
The question it answers Why did it happen, and how do we know?
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Recommendations
Numbered recommendations, each tied to a specific root or underlying cause and ranked against the hierarchy of control. A recommendation that answers no finding is cut, and a finding with no recommendation is explained.
The question it answers What will stop this recurring, and why that control?
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Corrective action plan
Each recommendation becomes an action with a named owner, a target date, a verification method and a status. This table is lifted straight into your corrective action register when the report is issued.
The question it answers Who does what, by when, and how will we know it worked?
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Statutory reporting, sign-off and close-out
Whether the event was reported under RIDDOR or to the HSA, with the reference and date. Investigator and management sign-off, the close-out verification date and the appendices (plans, photographs, interview records).
The question it answers Has every legal duty been met, and when did the file close?
Not sure your current reports would pass this checklist? Book a compliance consultation and a chartered consultant will review your reporting process against your statutory duties.
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Two documents, two clocks
The Statutory Notification Is a Separate Document
A report under RIDDOR 2013 in the UK, or a notification to the Health and Safety Authority in Ireland, tells the regulator that a reportable event occurred. It goes on the regulator's own form, runs on a fixed window from the date of the accident, and does not ask why. In Ireland the duty sits under the Safety, Health and Welfare at Work Act 2005 and the General Application Regulations.
The investigation report is your internal document. Neither regime prescribes a layout for it, but it is what an inspector asks to see when they follow up a notification, and what your insurer reads first, often before the true cost of the incident has fully surfaced.
| Question | Statutory notification | Investigation report |
|---|---|---|
| Purpose | Tells the regulator a reportable event occurred | Establishes the cause and the fix |
| Format | The regulator's own online form | Your document, structured to HSG245 |
| Deadline (UK) | Deaths and specified injuries notified without delay and reported within 10 days; over-7-day injuries within 15 days | No statutory deadline; target dates set in the terms of reference |
| Deadline (Ireland) | Absence of more than 3 consecutive days, excluding the day of the accident, within 10 working days; fatal accidents notified immediately | No statutory deadline; target dates set in the terms of reference |
| Explains why? | No | Yes, down to root cause |
Never hold the notification back until the report is finished. The windows start at the accident, and the investigation often runs on for weeks after the notification is due. Our RIDDOR guide sets out the UK reportable categories in full.
Where a prosecution or civil claim looks likely, speak to a solicitor about how the report is commissioned and circulated before the first draft goes out. That decision is much harder to change after the report exists.
Where reports fail
Six Drafting Mistakes Inspectors Pick Up First
We see the same faults when we review reports written in-house. None of them needs more investigation to fix. Each one needs the draft to be tested against its evidence before it is signed.
Stopping at “operator error”
It describes the event without explaining it. The report closes and the condition that set the operator up to fail stays live on site.
Blame words in the narrative
Phrases like “failed to”, “ignored” or “careless” turn a fact into a verdict. Witnesses read the report, and the next investigation gets shorter answers.
Opinion presented as fact
A finding with no evidence reference is an opinion. Inspectors and insurers test findings against the file, and one untraceable finding weakens the rest.
Actions with no owner or date
“Review procedures” and “raise awareness” are intentions. Without an owner, a date and a verification method, nothing on the list can be shown to be done.
Controls from the bottom of the hierarchy
Retraining, a reissued toolbox talk and more PPE are the cheapest controls and the weakest. If every action sits there, the analysis probably stopped too early.
Closing the report before the actions
A report marked closed while its actions are still open tells the next inspector the fix was never checked. We record close-out only once each action is verified.
From report to register
How the Report Feeds the Corrective Action Register
A report is only finished once its actions are closed. Section 09 of the outline is written in the same columns as the corrective action register, so every action moves across on the day the report is signed and nothing is retyped or lost.
We then feed the register into your next site audit and the next revision of your safety policy, so close-out is visible to your senior team and to an inspector on the revisit.
| Action | Root cause ref | Hierarchy level | Owner | Target date | Verification | Status |
|---|---|---|---|---|---|---|
| Redesign the changeover so it can be done with the guard in place | RC-1: production rate set without a guarded method | Engineering control | Named engineering manager | A fixed calendar date | Observed changeover on site, signed off | Open / verified closed |
Register columns, with an illustrative row based on the guard-removal example on our investigation page.
Related engagements
When the Report Needs a Chartered Author
Investigation and reporting sit inside our wider Safety Consulting service. The same chartered team that writes the report can run the audit and revise the policy the actions point to.
Accident Investigation
An independent CMIOSH-chartered investigator on site within 48 hours, guaranteed in writing, leading the root-cause analysis and writing the report.
Audits and Inspections
A gap-registered site safety audit that checks whether the corrective actions from a report have actually closed out on the ground.
Back to Safety Consulting
Return to the Safety Consulting hub to see all 6 chartered engagements, from CDM advisory through our health and safety legal advisory line.
What clients say
A Fresh Pair of Chartered Eyes
Operations and EHS leads at energy and utilities operators describe the independent view we bring to their sites. These are their words, verbatim.
“Coyle Group offers a fresh pair of eyes: he will often spot the potential for hazard.”
“Gavin has supplied competent EHS personnel… we want to go further, making all our plants safer.”
“Gavin is always a phone call away and has always provided a professional and supportive service… on many occasions at very short notice and outside of business hours.”
Questions about the write-up
Accident Investigation Report Questions Answered
What are the four key elements of an accident investigation report?
HSE guidance HSG245 builds an investigation around 4 steps, and a good report follows the same shape. Information gathering sets out what happened, when, where and who was involved. Analysis explains why it happened, down to immediate, underlying and root causes. Risk control measures identify which controls failed or were missing and what will replace them. The action plan sets out who does what, by when, and how completion is verified. We add document control, an executive summary, terms of reference, an evidence register and close-out sign-off around those four parts.
Is an accident investigation report the same as a RIDDOR report?
No. A RIDDOR report in the UK, or a notification to the Health and Safety Authority in Ireland, tells the regulator that a reportable event occurred. It goes on the regulator’s own form and runs on a fixed window from the date of the accident. The investigation report is your internal document that explains why the event happened and what you are changing. The notification should never wait for the investigation report, because the investigation usually runs on for weeks after the notification is due.
Who should write the accident investigation report?
HSG245 expects managers, supervisors and employee representatives to take part in the investigation, with more senior management involved as the investigation level rises. We recommend that whoever signs off the findings has no reporting line into the work being investigated, because that independence is what a regulator, an insurer or an inquiry looks for first. On our engagements a CMIOSH-chartered investigator writes the report and signs the findings under their own professional name.
Is there an HSE accident investigation template?
HSG245 includes a set of forms built around its four steps, and they are a sensible starting point for a low-level investigation. The limitation of any template is that it prompts you to fill boxes rather than prove a causal chain. For anything above a minimal-level event, use the ten-section outline on this page as a checklist and write the report for the event and the site. Every report we issue is written that way, never pulled from a template library.
How long should an accident investigation report be?
Long enough to answer the questions its terms of reference set, and no longer. A minimal-level investigation into a minor event may fit on a few pages. A high-level investigation into a serious injury or a dangerous occurrence runs longer, with the evidence, plans, photographs and interview records held in appendices so the main report stays readable. The investigation level graded at the start sets the length, whatever the volume of material collected.
How long should we keep an accident investigation report?
RIDDOR requires records of reportable incidents to be kept for at least 3 years, and the investigation report belongs on the same file. Many organisations keep investigation files for longer where a civil claim is possible or where the findings shape a safety policy still in force. Keep the report, the evidence register and the corrective action register together so the file tells the whole story if it is ever asked for.
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