Is my project notifiable? The F10 notification explained

Most small building jobs never need an F10. Some do, and it is easy to miss the point at which a job tips over the line, especially when the programme stretches or extra trades turn up. This guide sets out the test in the exact words of the regulations, how to count the days, who has to send the notice, when, and what happens to it once it is sent.

The Construction (Design and Management) Regulations 2015 (CDM 2015) apply to construction projects in Great Britain.

The test, word for word

Regulation 6(1) says a project is notifiable if the construction work on a construction site is scheduled to:

(a) last longer than 30 working days and have more than 20 workers working simultaneously at any point in the project; or (b) exceed 500 person days.

Three things are worth slowing down for.

• Limb (a) has two halves, and both must be met. A job that lasts 60 working days but never has more than 20 workers on site at the same time does not meet limb (a).
• Limb (b) stands on its own. If the job will exceed 500 person days, it is notifiable however many people are on site at once.
• "Scheduled to" matters. The test looks at what the work is planned to involve, not only what has happened so far.

How to count working days

CDM 2015 defines a working day as "any day on which construction work takes place" (regulation 2(1)). It is not limited to Monday to Friday.

HSE's CDM FAQs make the same point. Every day on which construction work is likely to be carried out should be counted, even if the work that day is short, including holidays and weekends. HSE's L153 guidance on the regulations (paragraph 47) says the same.

How to think about person days

CDM 2015 does not define "person days", and we have not found a worked example in HSE's current guidance pages, so we will not invent one here. What is clear is that limb (b) looks at the total amount of work planned, not just at how long the job runs or how many people are on site on the busiest day.

Base your figure on your own programme and labour plan, and count every trade, not just your own team. If the total is anywhere near 500, check it carefully, or take advice, before deciding the job is not notifiable.

Projects that grow

A job that starts small does not stay exempt just because it was not notifiable on day one. HSE's L153 guidance (paragraph 48) says that if a project is not notifiable at first, but later changes in scope mean it meets the criteria, the client must notify as soon as possible.

So if the scope or programme grows, revisit the numbers.

Who has to notify

Regulation 6(2) puts the duty on the client: where a project is notifiable, "the client must give notice in writing to the Executive". HSE's FAQs add that, in practice, the client may ask someone else to notify on its behalf. The duty still sits with the client.

Domestic clients are different. A domestic client is defined as a client for whom a project is being carried out which is not in the course or furtherance of a business of that client (regulation 2(1)). Under regulation 7(1), the client duties in regulations 4(1) to (7) and in regulation 6 must instead be carried out by:

• the contractor, where there is only one contractor;
• the principal contractor, where there is more than one contractor; or
• the principal designer, where there is a written agreement that the principal designer will fulfil those duties.

HSE's F10 page puts it simply. If the client is a commercial client, they must notify HSE. If the client is a domestic client, notification must be carried out by the contractor (or principal contractor if there is more than one), or by the principal designer where there is a written agreement.

So on a notifiable domestic job, the F10 is very likely to be your job as the contractor.

When to notify

Regulation 6(2) says the notice must be given "as soon as is practicable before the construction phase begins".

The construction phase is defined as the period beginning when construction work in a project starts and ending when it is completed (regulation 2(1)). In other words, the F10 should go in before work starts on site, not once you are already underway, unless the project only became notifiable later (see above).

How to notify: the online F10

HSE says you can notify a notifiable project using the online F10 form, and that it no longer processes paper forms or accepts notifications by email or post. HSE's L153 guidance calls the electronic F10 "the easiest way to notify any project".

Before you start, HSE says you must know the contact details for the client, the principal designer and the principal contractor. Once you submit, HSE sends a unique serial number which you can use to access or edit the notification later.

Single-contractor projects: HSE's F10 page says that, for a notifiable project with only one contractor, you should enter the sole contractor's name as both the principal designer and the principal contractor, and use the free text box to explain that it is a single-contractor project.

What goes on the F10

The required particulars are listed in Schedule 1 of CDM 2015. They include:

• the address of the site, or a precise description of its location, and the name of the local authority;
• a brief description of the project and the construction work it involves;
• contact details for the client, principal designer and principal contractor;
• the date planned for the start of the construction phase, and its planned duration;
• the time allocated by the client for the construction work;
• the estimated maximum number of people at work on site, and the planned number of contractors;
• the names and addresses of any contractors and designers already appointed; and
• a declaration signed by or on behalf of the client that the client is aware of the client duties.

Display it on site, and keep it current

Under regulation 6(3), the notice must:

• contain the particulars in Schedule 1;
• be clearly displayed in the construction site office in a comprehensible form where any worker engaged in the construction work can read it; and
• if necessary, be periodically updated.

L153 (paragraph 51) adds that the client can display it themselves or ask the principal contractor or contractor to do so. Changes can be made through HSE's edit facility using the serial number.

Railways and nuclear sites

Not every project goes to HSE. Under regulation 6(4) and (5), certain work for which the Office of Rail and Road is the enforcing authority is notified to that office instead. Work on certain nuclear and defence sites goes to the Office for Nuclear Regulation instead. If either applies, check regulation 6 in full.

Not notifiable does not mean CDM-free

This is the most important line in this guide. HSE's L153 (paragraph 52) is blunt: the requirements of CDM 2015 apply whether or not the project is notifiable. An F10 is a notice to the regulator. It does not create your CDM duties, and not needing one does not remove them.

This article is general information, not legal advice. CDM 2015 wording is quoted from legislation.gov.uk and HSE guidance as checked on 1 October 2026. Check the current text, or speak to a competent CDM adviser, before relying on it for a live job.