Submitting mandatory occurrence notices and reports
Source: gov.uk (2025-09-04)

A guide for principal designers, principal contractors and accountable persons to report incidents or risks of structural failure, or the spread of fire to the Building Safety Regulator.

Who must submit mandatory occurrence notices and reports

Principal designers and principal contractors

Principal designers and principal contractors must submit mandatory occurrence notices and reports, during:
- construction of a new higher-risk building
- work on an existing higher-risk building, including work that causes it to stop being a higher-risk building
- work on an existing building that will make it a higher-risk building
A higher-risk building is a building that has at least:
- 7 storeys or is at least 18 metres high
- 2 residential units or is a hospital or a care home
You can read guidance about the criteria that makes a building a higher-risk building. (https://www.gov.uk/government/collections/guidance-on-the-criteria-for-being-a-higher-risk-building)

Accountable persons

A higher-risk building with at least 2 residential units must be registered with the Building Safety Regulator (BSR) (https://www.gov.uk/guidance/applying-to-register-a-high-rise-residential-building) before people live there.

Accountable persons must submit mandatory occurrence notices and reports for the parts of the high-rise residential building they are responsible for.

What to report to BSR

You must submit a mandatory occurrence notice and report when a safety occurrence has caused, or would be likely to present a risk of:
- the death of a significant number of people
- serious injury that needs immediate treatment in hospital or causes a permanent or irreversible disabling condition to a significant number of people
Safety occurrence are incidents or risks involving:
- structural failure of the building
- fire safety (design and construction phase)
- the spread of fire or smoke in the building (occupation phase)
Unless they are remedied, safety occurrences would be likely to present a risk of serious harm to people when the building is in use and include both:
- an incident that has happened
- the risk of an incident happening in the future
You must submit a report even if the safety occurrence is remedied immediately. The only exception is when a principal contractor remedies issues to ongoing building work, which are unlikely to risk significant numbers of death or serious injury.

Failing to report

You’re committing an offence if you fail to make a report without a reasonable excuse and could face enforcement action, including prosecution.

If you know that a mandatory occurrence report has already been submitted to BSR, you do not need to submit a report for the same safety occurrence. You should obtain a copy of the report submitted to BSR to support your decision not to make the report yourself.

Reporting incidents to the fire service

If you report an incident to the fire service, you must also submit a mandatory occurrence notice and report if it meets the criteria of what to report to BSR. (#what-to-report-to-bsr)

Duties of principal designers and principal contractors

As a principal designer or principal contractor, you must submit mandatory occurrence notices and reports during construction or building work of higher-risk buildings.

The notices and reports relate to the building that is under construction or undergoing building work. They do not relate to safety incidents relating to the construction site in general or any temporary structures.

You must establish and operate a mandatory occurrence reporting system (https://www.gov.uk/guidance/operating-a-mandatory-occurrence-reporting-system) for others to report safety occurrences to you for review.

Find out more about the roles of principal designers and principal contractors in the guide design and building work: meeting building requirements (https://www.gov.uk/guidance/design-and-building-work-meeting-building-requirements).

Safety occurrence examples during the design and construction phase

Some safety occurrence examples that could meet the criteria of what to report to BSR, (#what-to-report-to-bsr) include, but are not limited to the following:

Structural failure

This includes:
- total or partial collapse of the building
- defective building work, including defective competent person scheme (https://www.gov.uk/building-regulations-competent-person-schemes) work which is part of the wider building work
- unexpected failure or the degeneration of construction materials or products in relation to load bearing
- the discovery of structural defects and the potential for the effect on load bearing
Fire safety

This includes fire safety issues concerning the:
- spread of fire and smoke
- means of escape from the premises in the event of a fire
- fighting of fires on the premises
- detecting of and warning of fire and smoke spread
- any other measures to mitigate the effects of fire and smoke
It also includes:
- the use of non-compliant products or incompatible products in the buildings construction to minimise or prevent the spread of fire
- inappropriate or incorrect installation of products to minimise or prevent the spread of fire
- product failure against specification and claimed performance to minimise or prevent the spread of fire
- faults in the design plans, caused by either design software or human error to minimise or prevent the spread of fire
Change control applications

If you submit a mandatory occurrence report, you may also need to make a change control application.

For example, during construction you discover the load points in the design plans have been miscalculated. If this is not remedied, it would be likely to present a risk of structural failure and risks death or serious injury to a significant number of people when the building is in use. This meets the criteria of what to report to BSR (#what-to-report-to-bsr,) and you must submit a mandatory occurrence notice and report.

To correct the plans, the principal contractor must also submit a change control application (https://www.gov.uk/guidance/making-changes-to-a-higher-risk-building-project) and request a major change to the building control application.

Transitional arrangements

If the higher-risk building in construction is subject to the transitional arrangements, you may not need to submit mandatory occurrence reports for it.

Read the transitional arrangements for the higher-risk regime factsheet (https://www.gov.uk/government/consultations/consultation-on-implementing-the-new-building-control-regime-for-higher-risk-buildings-and-wider-changes-to-the-building-regulations-for-all-buildings/outcome/government-response-to-the-consultation-on-implementing-the-new-building-control-regime-for-higher-risk-buildings-and-wider-changes-to-the-building-re#annex-b-transitional-arrangements-factsheet) to understand reforms to building work processes and their regulations.

Reporting of Injuries, Diseases and Dangerous Occurrences Regulations (RIDDOR)

During building work, if someone has died or has been injured because of a work-related incident you may need to make a RIDDOR report. For example, if someone has fallen from scaffolding and has died.

If an incident is reported under RIDDOR, you must also submit a separate mandatory occurrence notice and report if the incident meets the criteria of what to report to BSR (#what-to-report-to-bsr).

For example, during building work, part of a building collapses and injures people. The principal contractor reports the incident under RIDDOR. The principal contractor also submits a mandatory occurrence notice and report, as the incident involves structural failure, which if not remedied would be likely to present a risk of death or serious injury to a significant number of people when the building is in use.

You can find out about what must be reported under RIDDOR (https://www.hse.gov.uk/riddor/index.htm) on the HSE website.

Duties of accountable persons

As an accountable person (https://www.gov.uk/guidance/safety-in-high-rise-residential-buildings-accountable-persons), you must submit mandatory occurrence notices and reports to BSR for the parts of the high-rise residential building you are responsible for.

Safety occurrence examples

Some safety occurrence examples that could meet the criteria of what to report to BSR (#what-to-report-to-bsr) when the building is occupied by residents, include, but are not limited to the following:

Structural failure

This includes:
- total or partial collapse of the building
- defective building work, including defective competent person scheme (https://www.gov.uk/building-regulations-competent-person-schemes) work which is part of the wider building work
- unexpected failure or the degeneration of construction materials or products in relation to load bearing
- the discovery of structural defects and the potential for the effect on load bearing
Fire spread

This includes:
- failure of materials between different compartmented areas of the building on the same level, above or below and this would include internally from within the building to the external façade or wall and vice versa
- failure of systems to automatically prevent fire spread when in use such as sprinkler and foam systems where required or provided
- failure of fire-fighting equipment designed to prevent spread when in use, such as dry risers and wet risers
- failure of an automatic opening vent (AOV) or other smoke extraction when in use and smoke spreads from one compartment or area to another
- failure of fire doors and seals to minimise or prevent the spread of fire
- inappropriate or incorrect installation of fire safety products design to minimise or prevent the spread of fire
- failure against specification and claimed performance of fire safety products design to minimise or prevent the spread of fire
The principal accountable person must establish and operate a mandatory occurrence reporting system (https://www.gov.uk/guidance/operating-a-mandatory-occurrence-reporting-system) for residents and others to report safety occurrences to the accountable persons.

Safety case report

All safety occurrences should be included in the building’s safety case report. (https://www.gov.uk/guidance/preparing-a-safety-case-report)

Safety occurrences before January 2024

If a safety occurrence was identified before January 2024, you must make a mandatory occurrence notice and report if one of the following applies:
- after taking into account any safety measures that are in place, it still meets the criteria of what to report to BSR (#what-to-report-to-bsr)
- the risk has worsened and now meets the criteria
When to report to BSR

When a safety occurrence happens or is identified that meets the criteria of what to report to BSR (#what-to-report-to-bsr) you must submit a:
- notice as soon as you can
- report within 10 calendar days of the safety occurrence being identified
How to report to BSR

You can submit a mandatory occurrence notice and report online (https://www.gov.uk/guidance/submit-a-mandatory-occurrence-notice-and-report).

Submit a notice

BSR will ask you for:
- your contact details
- the address of the building where the incident or risk has been identified
- the date the incident or risk was identified
- a brief description of the incident or risk
- any immediate actions you’ve taken to keep people safe
When you submit a notice, BSR will give you a reference number which you can use to submit a mandatory occurrence report.

Submit a report

You must submit a report after submitting your notice. You can give BSR the full report immediately after submitting the notice if you have the information available.

BSR will ask you for:
- your mandatory occurrence notice reference number
- the building registration application reference or address if the building is occupied
- the building control application reference number if the building is in design or construction and construction work has started
- your contact details, the name of your organisation and its involvement in the building
- the incident or risk you are reporting and when and how you became aware of it
- what happened, or has the potential of happening
- who is involved and the effect on them
- what you have done and plan to do to keep people safe
- any supporting information, such as documents, videos or photos
Missing information

If you intend to gather more information after submitting the report, tell BSR when you expect to have it. BSR will also contact you if any extra information is needed.

Other ways to report

Telephone: xx-xxxx-xxxx

Monday to Friday, 8:30am to 5pm (except Wednesdays when we are open from 10am to 5pm, and public holidays when we are closed).

If you would prefer to speak to us on the phone in a language other than English, a translation service is available.

Standard call charges (https://www.gov.uk/call-charges) will apply.

After submitting a report to BSR

BSR will review the report and determine the severity of the safety occurrence. BSR will also review any safety measures that are in place, and if they are sufficient to manage the risk.

BSR will contact you if:
- further information is needed
- they decide the incident or risk did not need to be reported
- they need to start an investigation
During an investigation, BSR will review the findings and decide if any action is needed.

There are no charges for making a mandatory occurrence notice and report, but investigations do incur cost recovery charges. You can find out more about BSR’s charging scheme (https://www.hse.gov.uk/building-safety/charging-scheme.htm) on the HSE website.

Provision of false of misleading information

You’re committing an offence if you knowingly or recklessly provide information that is false or misleading to BSR to avoid any enforcing action being taken and could face enforcement action including prosecution.

Ensure your information is correct and accurate to the best of your knowledge.

Obstructing a BSR authorised officer

You may commit an offence if you intentionally obstruct an authorised officer of BSR exercising a relevant building function and could face enforcement action including prosecution.

Assist BSR by providing the required information with as much detail as possible, so that your mandatory occurrence report can be assessed effectively. Insufficient or omitted details may need further investigation by BSR which could incur additional charges.

The information on this page is not intended to be guidance under section 108 of the Building Safety Act 2022. (https://www.legislation.gov.uk/ukpga/2022/30/section/108/enacted)