Mandatory Occurrence Reporting Guidance
Clear, plain-English guidance for dutyholders under the Building Safety Act
Mandatory Occurrence Reporting (MOR) is a legal requirement introduced under the Building Safety Act 2022. It is designed to ensure serious fire and structural safety risks are identified early, assessed properly, and reported transparently to the Building Safety Regulator (BSR).
MOR is not a blame tool and it is not optional. It is an early warning system that supports accountability, learning, and confident decision-making when safety risks arise.
What often makes MOR difficult in practice is not understanding the requirement, but sustaining it over time. Reporting systems decay, actions fragment, and evidence becomes harder to retrieve as people, contractors, and priorities change.
NBR’s approach recognises that building safety does not stop at registration or inspection. We support ongoing stewardship by helping organisations manage MOR information, actions, and evidence as part of a living safety record, across a building or portfolio, rather than leaving dutyholders to rebuild assurance each time an issue arises.
This guidance is written for Principal Accountable Persons, Accountable Persons, and others who hold responsibility but may not work day to day in building safety. It explains what MOR is, when a report must be made, and how a practical reporting system should operate in reality.
What is Mandatory Occurrence Reporting
Mandatory Occurrence Reporting requires dutyholders to have a clear and reliable way for safety concerns to be raised, recorded, assessed, and where required, reported to the Building Safety Regulator.
If a safety issue could lead to serious harm, it must be reported, recorded, and acted on. It must not be ignored, parked, or lost in informal communication channels.
MOR supports a culture of openness where risks are surfaced early, evidence is gathered while it is fresh, and decisions remain traceable over time.
Who must operate a Mandatory Occurrence Reporting system
Mandatory Occurrence Reporting applies to occupied Higher-Risk Buildings (HRBs) in England and forms part of the ongoing building safety management regime under the Building Safety Act.
For occupied buildings, MOR forms part of the wider safety management framework and sits alongside the Safety Case as a live, ongoing process, not a one-off compliance activity.
Key roles include:
Principal Accountable Person (PAP)
Must establish and operate a single MOR system for the building and ensure it is reviewed regularly so it remains effective.
Accountable Person (AP)
Must assess safety occurrences relating to the parts of the building they are responsible for and submit mandatory occurrence notices and reports to the BSR when the reporting threshold is met.
Principal Designer and Principal Contractor
Where building work is being carried out to an occupied Higher-Risk Building, MOR duties also apply to the Principal Designer and Principal Contractor for the duration of those works.
Where there is more than one Accountable Person, each remains responsible for their part of the building. The PAP ensures there is a single reporting route so issues do not fall between organisational boundaries.
What counts as a reportable safety occurrence
A safety occurrence is an incident that has happened, or a risk that could happen, relating to:
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Structural failure, or
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Fire safety, including fire or smoke spread
A safety occurrence becomes reportable when it has caused, or is likely to present, a risk of serious harm to a significant number of people. This includes the risk of death or serious injury requiring immediate hospital treatment.
An issue must still be reported even if it is fixed immediately. MOR is about transparency and learning, not just the final outcome.
If there is uncertainty about whether an issue meets the reporting threshold, it should be recorded and assessed promptly. A clear, evidenced decision is always preferable to an unrecorded assumption.
When and how to report to the Building Safety Regulator
Reporting takes place in two stages:
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Mandatory occurrence notice This must be submitted as soon as you can after identifying a reportable safety occurrence. It is the initial alert to the BSR.
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Mandatory occurrence report This must be submitted within 10 calendar days and provides fuller detail and supporting evidence.
The notice must not be delayed while further information is gathered. The full report can follow once details are confirmed.
How to operate an MOR system in practice
For Principal Accountable Persons, a well-run MOR system should:
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Make reporting simple for residents, staff, and building users
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Ensure reports are recorded consistently so nothing is lost
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Ensure reports are assessed promptly by the relevant Accountable Person
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Ensure the BSR is notified when the reporting threshold is met
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Create a reliable evidence trail that supports the Safety Case
An MOR system should be structured, proportionate, and repeatable, and capable of being maintained consistently over time. It should not rely on inboxes, ad-hoc decisions, or individual memory.
Record keeping, the Safety Case, and the Golden Thread
Mandatory Occurrence Reporting is closely linked to the Safety Case and Golden Thread information.
Each safety occurrence should be recorded in a structured way so it is clear:
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What happened or what risk was identified
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What immediate actions were taken to keep people safe
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Whether it met the MOR reporting threshold
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What was reported to the BSR and when
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What remedial actions were completed
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What learning resulted and what has changed
Good record keeping supports regulatory confidence and long-term assurance. Poor records undermine confidence even where actions were taken correctly.
Download the Mandatory Occurrence Reporting guide
The Mandatory Occurrence Reporting guide includes:
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Plain-English explanations of MOR responsibilities
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Practical examples of reportable safety occurrences
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Templates for mandatory occurrence notices and full reports
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An MOR log for internal control and audit trail
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Optional investigation and lessons learned templates
Our approach
NBR guides are published to support clarity, consistency, and confidence across the property sector.
They reflect publicly available legislation and statutory guidance and are intended to support understanding and good practice. They are not legal advice and should always be read alongside the latest guidance published by the Building Safety Regulator and GOV.UK.
Where information is structured, accessible, and maintained over time, Mandatory Occurrence Reporting becomes a calm, predictable process rather than a reactive one.
More building safety guidance
Explore our full Knowledge Hub for guidance on Safety Cases, risk management, dutyholder responsibilities, and Building Safety Regulator expectations.