F10 notification guide: when and how to notify HSE

An F10 is the online notification to the Health and Safety Executive for a construction project that meets the CDM 2015 notification threshold. It tells HSE about the project; it is not an approval to begin, a permit to work or proof that the construction phase plan and other CDM duties have been met. The client should assess likely duration and staffing early enough to notify before construction work starts. If an initially non-notifiable project changes scope and becomes notifiable, the duty must be revisited promptly.

HSE's CDM frequently asked questions and F10 guidance are the primary references. This guide is about the notification decision and form workflow, not a full CDM compliance guide. It uses Great Britain HSE terminology and should not be assumed to cover a different regulator or jurisdiction.

The two notification tests

A construction project is notifiable if the construction work is expected to:

1. Last longer than 30 working days and have more than 20 workers on site at the same time at any point; or
2. Exceed 500 person-days of construction work.

The first test requires both the duration and simultaneous-worker conditions. Thirty days alone is not enough. Twenty workers in total across the whole project is not the same as more than 20 at the same time. The second test is an alternative; a project can cross 500 person-days without ever having 21 workers together. HSE says days on which construction work is likely to occur count even if the work that day is short, including weekends and public holidays. Work from the realistic programme, not a deliberately low estimate.

Example A: a six-week refurbishment with 12 workers each day may exceed 30 working days but does not meet the first test because it never has more than 20 simultaneously. It could still exceed 500 person-days if the total days worked by all workers is high enough. Example B: a project with 22 workers on one day and 25 working days does not meet the first test because it is not expected to last longer than 30 working days; check the 500-person-day total separately. These are simplified calculations. Count the actual planned construction workforce and working days for the whole project, including relevant contractor teams, then revisit the estimate as plans evolve.

Who has to notify?

For a commercial client, HSE says the client has the duty to notify. A person acting for the client may help complete the form, but the client should verify the accuracy and retain the record. A principal contractor should not be described as the universal legal owner merely because it often administers paperwork. HSE's F10 page explains the domestic-client route: the contractor, or principal contractor if there is more than one contractor, notifies; a principal designer may do so where a written agreement gives them the client duties. Identify the correct dutyholder for the actual project before submission.

If several organisations call themselves “the client,” determine who is commissioning the construction project and who carries CDM client duties. Record the agreed contacts. If the project has more than one contractor, the client must also deal with principal-designer and principal-contractor appointments under CDM 2015. Notification is a separate requirement and does not make those appointments on its own.

Gather information before opening the form

HSE's F10 service accepts an initial notification and later edits, withdrawal and PDF retrieval. Its public F10 guidance says to know the contact details for the client, principal designer and principal contractor. Before opening the online form, assemble a short project fact sheet:

• Project title, site address and description of construction work.
• Client legal name and contact, plus the person authorised to submit on its behalf if relevant.
• Principal designer and principal contractor names and contacts, where appointed.
• Planned start and duration, peak number of people on site, and estimated person-days.
• The calculation showing which notification test is met.
• The project email address that should receive and retain the acknowledgement.
• A named person who will update the F10 if key details change.

Check these against the actual project programme and appointments. Do not insert a supplier's sales contact as the client or guess a principal contractor before one is selected. The online service itself controls the final required fields, so verify the current form on the day of submission. HSE warns that a form session can time out after inactivity; prepare facts first rather than researching them in the form.

Submit through HSE and keep the acknowledgement

Use the current HSE F10 notification page to reach the official form. HSE says it no longer processes paper F10s or accepts notification by email or post. After submission, HSE sends a unique serial number that is needed to access or edit the notification. Save the acknowledgement, submitted PDF or record, serial number and date in the controlled project file. Check that the intended client has access to the email and record; a form submitted from a temporary consultant account can be difficult to maintain later.

For a notifiable commercial project, HSE's commercial-client guidance says a copy of the notification must be displayed in the construction site office. Confirm where and how the site team will display the current version. That display is a project control; it does not replace communicating hazards, welfare arrangements, pre-construction information or the construction phase plan.

Do not wait for HSE to “approve” an F10 before planning safe work. HSE notification is not design or method approval. The client and other dutyholders still have to make suitable arrangements under CDM 2015 for any construction project, including projects below the F10 threshold.

Update or withdraw when facts change

Project programmes change. If the initial duration or workforce estimate was below the threshold but later scope takes it over either test, HSE's CDM guidance L153 says the client must notify as soon as possible when the project becomes notifiable. Do not treat the initial estimate as an eternal exemption. Assign someone to watch the programme and contractor headcount at meaningful milestones.

If a submitted F10 needs an update, use HSE's edit-notification service. It asks for the client email and notification number. Review changes before submitting again, preserve the updated record and make sure the site copy is current. If a project is cancelled or a notification must be withdrawn, use HSE's current official process rather than simply deleting the local PDF. Keep a record of the reason and person who made the change.

A practical update trigger list includes new client contact; principal designer or principal contractor change; major revised dates, duration or site arrangements; substantially changed scope; and a workforce forecast that changes the notification decision. The HSE form instructions govern what must be updated; this is a management checklist, not a claim that every minor schedule slip requires a fresh submission.

Common errors to avoid

Confusing “more than 20” with “20 or more.” The first threshold uses *more than* 20 simultaneous workers and more than 30 working days. Count all relevant contractors likely to be present together; do not count only direct employees of the principal contractor.

Forgetting the alternative 500-person-day test. A long project with modest daily workforce can still be notifiable.

Treating F10 as the trigger for all CDM duties. CDM planning and risk-management duties apply to construction work even below notification thresholds. A construction phase plan is required for every construction project; its scale should suit the project.

Submitting through the wrong channel. Use HSE's current form, not an old PDF, email or a third-party calculator. A free checker can help estimate the threshold but does not submit the legal notice.

Losing the notification number. Without it and the correct client email, updates become harder. Store them in a controlled project record accessible to the dutyholder.

Leaving a stale site copy. If the form changes, update the displayed and stored version so site teams and HSE see the same project facts.

Where Complys fits

The observed Complys CDM 2015 duty checker offers an F10 threshold check, and its CDM 2015 guide covers the broader CDM framework. These are relevant internal links after their current claims and canonical host are checked. They do not replace HSE's form. A buyer may ask Complys to demonstrate current project records and reminder features; do not claim that it submits, edits or withdraws F10 notifications with HSE unless implementation evidence confirms this. Some live Complys marketing describes broad automated CDM coverage and tender features; treat those as unverified product claims rather than importing them into this guide.

The page's own search intent is narrow: recognise a notifiable project, identify the dutyholder, complete the official notification, preserve it and keep it current. Keep broad CDM role explanations with the existing CDM owner to avoid cannibalisation.

Source and writer-side QA record

Intent/cannibalisation: Existing Complys CDM guide and duty checker cover threshold overview; this proposed guide owns the *F10 submission workflow*. Public search on 6 October 2026 found no exact Complys page at the proposed route; repository check remains a publication gate. Product truth: no HSE form integration or submission claim. Internal links: observed .co.uk URLs, confirm repository canonical. Writer-side disposition: READY.