Guide
F10 notification: when is a project notifiable?
The detailed guide behind this calculator: the thresholds, who notifies, what the notice contains, and displaying and updating it.
Free CDM tool
F10 Notification Calculator
Check whether your planned construction work is likely to meet either of the CDM 2015 Regulation 6 notification thresholds, and see exactly which test is met.
Takes about 1 minute · No sign-up required
Does your project need an F10 notification?
Enter three figures to check whether your project meets the CDM 2015 notification thresholds.
When is an F10 notification required? The thresholds in figures
A construction project is notifiable under Regulation 6 of CDM 2015 where the construction work is scheduled to last longer than 30 working days and have more than 20 workers working simultaneously at any point, or to exceed 500 person-days. Either test is enough on its own. The first test is an and: a long programme by itself does not make a project notifiable. Regulation 6, CDM 2015: notification of a construction project, including the thresholds, timing, display and update requirements (opens in a new tab)
So a long project with a small crew is not notifiable on duration alone, and a large crew on a short programme is not notifiable on headcount alone — both parts of the first test have to be true together. The person-day test is independent and can make a project notifiable by itself.
The two F10 notification thresholds
Both tests side by side, with the exact wording each one turns on:
| Test | Requirement |
|---|---|
| Duration and workforce | More than 30 working days and more than 20 workers working simultaneously at any point in the project. Both parts must be true together. Regulation 6(1)(a). |
| Person-days | More than 500 person-days of construction work, whatever the duration or the peak workforce. Regulation 6(1)(b). |
For the wider picture — what the notice must contain, when it must be given, and how it is displayed and kept current — see the F10 notification guide.
How the F10 Notification Calculator works
The calculator turns Regulation 6 into three plain figures and applies each test separately, so you can see which one your project met.
- Step 1
Enter planned working days
The number of days on which construction work is expected to take place — not the calendar span of the project.
- Step 2
Enter peak simultaneous workers
The highest number expected to be working at the same time at any point, not the total number who will work on the project.
- Step 3
Check person-days where needed
Enter a known total from your programme, or use the quick estimate based on the average workforce per working day.
The two Regulation 6 tests are evaluated separately, and the result shows which was met and which was not. Where the duration and workforce test is already met, person-days can be left blank, because they cannot change the answer.
The calculator never uses your peak workforce as the average workforce. They are different figures, and substituting one for the other would overstate the person-day estimate.
F10 notification examples
These worked examples show how the strict boundaries behave with real figures. Each row is the same calculation the tool performs.
| Example | Working days | Peak workers | Person-days | Result |
|---|---|---|---|---|
| A | 30 | 21 | 500 | Not notifiable on these figures |
| B | 31 | 20 | 500 | Not notifiable on these figures |
| C | 31 | 21 | 500 | Notifiable — duration and workforce threshold |
| D | 10 | 5 | 501 | Notifiable — person-day threshold |
| E | 60 | 25 | 900 | Notifiable — both thresholds |
A and B both fail the first test, for opposite reasons. A reaches 30 working days but does not exceed them, so the duration part is not satisfied even though 21 workers clears the workforce part. B exceeds 30 working days but peaks at exactly 20 simultaneous workers, so the workforce part is not satisfied. Neither reaches 501 person-days, so the second test does not carry them either.
C clears both parts of the first test by a single day and a single worker, which is all it takes. D is notifiable on person-days alone despite a short programme and a small crew — a useful reminder that the second test stands by itself. E meets both, although either would have been enough.
What is a person-day for F10 notification?
A person-day is one person carrying out construction work for one working day. Ten workers on site for one working day is ten person-days.
Ten workers across 50 working days is 10 × 50 = 500 person-days. That lands exactly on the threshold, and Regulation 6 requires the construction work to exceed 500 person-days, so a project at exactly 500 is not notifiable on this test. A single additional person-day would change that.
Where you do not have a programme-derived total, the calculator can estimate one: working days × average workers per working day = estimated person-days. It shows the arithmetic with your own figures, so an unrealistic average is easy to spot.
What counts as a working day for F10?
A working day is a day on which construction work is scheduled to take place. HSE guidance counts every day on which construction work is likely to be carried out, including weekends and bank holidays where work is planned on them, and even a short spell of construction work on a day counts that day. HSE CDM FAQs: HSE guidance on counting working days for the notification threshold (opens in a new tab)
Three durations are easy to confuse, and only one of them is the figure this test uses:
- Calendar duration — the elapsed time from start to finish, including days when no construction work happens. Not the figure to use.
- Design or pre-construction programme — Regulation 6 measures the construction work, not the design phase that precedes it.
- Working days — the days on which construction work is actually scheduled. This is the figure the threshold uses.
A refurbishment spread across four calendar months, with construction work scheduled on 28 of those days, has 28 working days for this test — not 120.
Who submits an F10 notification?
Regulation 6 places the duty to give notice on the client. Regulation 7 changes who carries out that duty on a domestic project. Regulation 7, CDM 2015: application to domestic clients, including who carries out the client duties (opens in a new tab)
Commercial projects
The client must give notice in writing as soon as is practicable before the construction phase begins. The duty stays with the client even where a consultant, designer or contractor prepares and submits the notice on their behalf.
Domestic projects
Under Regulation 7 the client duties, including notification, are 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.
What happens if an F10 notification is required?
- Notify using HSE's official online service, in writing and as soon as is practicable before the construction phase begins.
- Keep the confirmation and any reference or serial information returned, so the project record shows when notice was given.
- Display an up-to-date copy clearly in the construction site office, in a comprehensible form where any worker engaged in the construction work can read it.
- Update the notification periodically where necessary, for example where the project particulars change.
Both links open HSE's own website in a new tab. Aptoris is not affiliated with HSE and does not submit notifications on your behalf.
Does a project have to be F10 notifiable for CDM 2015 to apply?
No. CDM 2015 can apply in full to a project that meets neither notification threshold. Notification and applicability are separate questions, and a great many CDM projects are never notifiable.
F10 status does not decide any of the following:
- whether CDM 2015 applies to the project at all
- whether a construction phase plan is required — one is required for every construction project, notifiable or not
- whether Principal Designer and Principal Contractor appointments are required, which turn on whether more than one contractor is involved
- whether the client duties apply
F10 Notification Calculator FAQs
What is an F10 notification?
An F10 notification is the written notice that must be given to the enforcing authority before construction work begins on a notifiable project, under Regulation 6 of CDM 2015. It sets out who is involved and what the project is. The F10 notification guide covers what the notice must contain.
When is an F10 notification required?
Where the construction work is scheduled to last longer than 30 working days and have more than 20 workers working simultaneously at any point, or to exceed 500 person-days. Either test on its own is enough to make the project notifiable.
Is a project lasting exactly 30 working days notifiable?
Not on the duration and workforce test. Regulation 6 requires the work to last longer than 30 working days, so exactly 30 does not cross it, however many workers are on site. The project could still be notifiable if it exceeds 500 person-days.
Does having more than 20 workers automatically make a project notifiable?
No. More than 20 simultaneous workers only counts alongside a programme longer than 30 working days, because the first test needs both parts. A short project with a large crew can still be notifiable, but on the person-day test rather than this one.
Is exactly 500 person-days notifiable?
No. Regulation 6 requires the construction work to exceed 500 person-days. A project calculated at exactly 500 — 10 workers across 50 working days, for example — falls below the threshold. 501 person-days crosses it.
Does a project need to meet both F10 notification tests?
No. The two tests are independent and either one is sufficient on its own. Meeting both does not change what has to be done; the project is notifiable as soon as either test is met.
How do I calculate person-days for an F10?
Add up the worker-days of construction work across the whole construction phase: one person working for one working day is one person-day. Where you have no programme total, multiply working days by the average number of workers per working day — the average across the phase, not the peak.
Can a single-contractor project be F10 notifiable?
Yes. Notification turns on duration, simultaneous workers and person-days, never on how many contractors are involved. The number of contractors decides whether Principal Designer and Principal Contractor appointments are required, which is a separate question.
Who submits the F10 on a domestic project?
Under Regulation 7 the client duties, including notification, are 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. See domestic projects for how these arrangements work in practice.
Does CDM 2015 still apply if an F10 is not required?
Yes. CDM 2015 can apply in full to a project that is not notifiable. A construction phase plan is required for every construction project, and the client duties apply regardless of F10 status. Use the Does CDM Apply? checker for that separate question.
Is the Aptoris F10 calculator an HSE calculator?
No. Aptoris is not HSE, and this calculator is not produced, approved or endorsed by HSE. It applies the published CDM 2015 Regulation 6 thresholds to the figures you supply, and it does not submit anything on your behalf. HSE guidance and the Regulations themselves remain the authoritative sources.
Checked against official F10 guidance
This calculator applies the notification thresholds in Regulation 6 of the Construction (Design and Management) Regulations 2015, together with current HSE F10 guidance. It is guidance based on the figures you enter, not a compliance determination, and the sources below remain authoritative.
- Regulation 6, CDM 2015: notification of a construction project, including the thresholds, timing, display and update requirements (opens in a new tab)
- Regulation 7, CDM 2015: application to domestic clients, including who carries out the client duties (opens in a new tab)
- HSE CDM FAQs: HSE guidance on counting working days for the notification threshold (opens in a new tab)
- HSE F10 guidance: who notifies, and how the online notification service is used (opens in a new tab)
- HSE online F10 service: the official service for making a notification (opens in a new tab)
Last reviewed:
Read more on F10 notification
This calculator checks the thresholds. The guides explain the detail behind them.
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Does CDM Apply?
A separate question from notification. Work through whether CDM 2015 is likely to apply to your project at all.
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