How to Investigate a Workplace Accident: A Step-by-Step Guide

No business wants to deal with an accident at work, but when one happens, how you respond makes all the difference. A good investigation does more than tick a box. It helps you understand what went wrong, protects your people from it happening again, and shows regulators that you take your responsibilities seriously.

Here is the approach we use when investigating accidents and incidents, based on HSE guidance (HSG245) and years of experience on sites across Kent and beyond.

Step 1: Make the scene safe and look after people

The first priority is always people. Make sure anyone injured receives first aid or medical attention, and that the area is safe so nobody else gets hurt. If there is a risk to the environment, such as a spill or release, take steps to contain it straight away.

Once everyone is safe, secure the scene as far as you reasonably can. Avoid moving equipment or clearing up unless it's needed for safety, as the scene holds valuable evidence.

Step 2: Report it where required

Some incidents must be reported to the HSE under RIDDOR (the Reporting of Injuries, Diseases and Dangerous Occurrences Regulations). This includes deaths, specified serious injuries, injuries that keep someone off normal duties for more than seven days, certain occupational diseases and dangerous occurrences. Deaths and specified injuries must be reported without delay.

If the incident has caused pollution or an environmental risk, you may also need to notify the Environment Agency. Don't forget internal reporting too, and record the incident in your accident book.

Step 3: Gather the information

This is where the investigation really begins. Collect as much information as possible while it's still fresh. This usually includes photographs and measurements of the scene, statements from the injured person and any witnesses, and relevant documents such as risk assessments, method statements, training records, permits to work and maintenance logs.

When speaking to witnesses, keep it relaxed and open. The aim is to understand what happened, not to find someone to blame. People are far more honest when they don't feel under attack.

Step 4: Analyse what happened and why

With the facts gathered, the next step is to work out the sequence of events and, most importantly, the causes. It helps to think in three layers.

The immediate cause is the direct reason the accident happened, such as a slip on a wet floor or an unguarded machine. Underlying causes are the conditions that allowed it, such as poor housekeeping, inadequate training or a missing check. Root causes are the management and organisational failings behind it all, such as a risk assessment that was never reviewed or a culture where shortcuts were accepted.

Stopping at the immediate cause is one of the most common mistakes. If you only fix the surface problem, the same accident is likely to happen again in a different form.

Step 5: Decide on the right controls

Once you understand the causes, identify what needs to change. Use the hierarchy of control: can the hazard be removed altogether? If not, can it be substituted, engineered out or isolated? Procedures, training and PPE all play a part, but they should support stronger controls rather than replace them.

Step 6: Create and follow through on an action plan

Every recommendation should become a clear action with a named owner and a realistic deadline. This is where many investigations fall down. A report sitting in a drawer protects nobody.

Review progress regularly, check that the changes are working in practice, and update risk assessments and procedures to reflect them.

Step 7: Share the learning

Finally, make sure the lessons reach everyone who needs them. Brief staff and supervisors, discuss the findings at toolbox talks or team meetings, and consider whether the same risk exists elsewhere in your business. Sharing what you've learned openly builds trust and strengthens your safety culture.

Getting expert support

An independent investigation can be especially valuable after a serious incident, when emotions are running high or when the HSE or Environment Agency are involved. An outside view helps get to the real causes and gives your action plan credibility.

If you need support with an accident investigation, regulator enquiries or reviewing your health and safety arrangements, get in touch with the team at Safety First.