Mental Health Act sections, explained
Who does what in the room, what sections 2, 3, 136 and the holding powers actually authorise, and what the 2025 Act changes.
Most clinicians working in mental health will be present at an assessment under the Mental Health Act long before they understand who in the room is doing what, and which decisions are legally theirs to make.
This is a plain account of the framework in England and Wales, written for the clinician whose job is to document rather than to decide.
This is orientation, not legal advice, and it is not a substitute for the Code of Practice, local policy, or the training required to hold any of these roles. Detention is a statutory act with serious consequences for a person's liberty. If you are unsure of your role, ask before acting.
Who can do what
Admission under the civil sections of the Mental Health Act 1983 requires an application and two medical recommendations, and the professionals involved are specified by the Act rather than chosen by convenience.
The Approved Mental Health Professional
The AMHP makes the application. They are usually a social worker, but may be a nurse, occupational therapist or psychologist with the approval training. A doctor cannot be an AMHP. The AMHP's role is not administrative: they must interview the person in a suitable manner and satisfy themselves that detention is the least restrictive appropriate option.
The doctors
Two medical recommendations are needed for sections 2 and 3. At least one doctor must be approved under section 12 of the Act — meaning they have recognised experience in diagnosing and treating mental disorder, in practice usually a psychiatrist. Wherever practicable, one doctor should have previous acquaintance with the person.
The nearest relative
Under the 1983 Act as it currently stands, the AMHP must consult the nearest relative, a person defined by a statutory hierarchy rather than chosen by the patient. This is one of the areas the 2025 Act changes, and it is discussed below.
An assessment is not the opinion of one person. Your documented findings feed into decisions made by professionals with specific statutory roles. Writing a description they can rely on is more useful than writing a conclusion, and it is what your role actually calls for.
The sections you will encounter
| Section | Purpose | Duration | Who is required |
|---|---|---|---|
| 2 | Admission for assessment | Up to 28 days, not renewable | AMHP application, two doctors, one section 12 approved |
| 3 | Admission for treatment | Up to 6 months, renewable | AMHP application, two doctors, one section 12 approved |
| 4 | Emergency admission where waiting for a second doctor would cause undesirable delay | Up to 72 hours | AMHP application, one doctor |
| 5(2) | Holding an existing inpatient | Up to 72 hours | The doctor in charge, or their nominated deputy |
| 5(4) | Nurse's holding power | Up to 6 hours | A registered mental health or learning disability nurse |
| 135 | Warrant to enter premises | To convey to a place of safety | Magistrate's warrant, executed with an AMHP and doctor |
| 136 | Removal from a public place | Up to 24 hours, extendable by 12 | Police officer |
The distinction between section 2 and section 3 causes the most confusion. Section 2 is for assessment where the diagnosis or the appropriate treatment is not yet established. Section 3 is for treatment where the condition is already known. A person on a first presentation with an unclear picture is a section 2 situation; someone with an established diagnosis relapsing in a familiar way may be a section 3 one.
Section 136 and the place of safety
Section 136 gives a police officer the power to remove a person who appears to be suffering from a mental disorder, and to be in immediate need of care or control, from a place to which the public have access, and to take them to a place of safety so that a mental health assessment can be arranged.
Several points are worth knowing because they shape the documentation.
- Since the Policing and Crime Act 2017, a police station may only be used as a place of safety for an adult in exceptional circumstances, and never for anyone under 18.
- The officer must, if practicable, consult a doctor, nurse or AMHP before exercising the power.
- The maximum period is 24 hours, extendable by up to 12 further hours where a doctor certifies that assessment could not be completed.
- Section 136 is not a form of admission and does not authorise treatment. It authorises detention for the purpose of assessment.
When someone arrives under section 136, an account of the events leading to detention will usually come from police officers. Record it as their account, attributed, and record separately what the person says about the same events. Where these differ, the difference is often the most significant thing in the record — and it is lost entirely if both are merged into one narrative.
Holding powers: 5(2) and 5(4)
These apply only to people already admitted as inpatients, and they exist to prevent someone leaving before a full assessment can be arranged.
Section 5(2) is used by the doctor in charge of the patient's treatment or their nominated deputy, and lasts up to 72 hours. It is not renewable, and the clock starts when the report is delivered to the hospital managers.
Section 5(4) is the nurse's holding power, lasting up to six hours, available to a registered mental health or learning disability nurse where a doctor cannot attend immediately. It ends as soon as a doctor with 5(2) powers arrives.
Neither applies in an emergency department, since a person attending A&E has not been admitted. That distinction catches people out regularly.
What the Mental Health Act 2025 changes
The Mental Health Bill received Royal Assent on 18 December 2025, becoming the Mental Health Act 2025. It amends rather than replaces the 1983 Act, and follows the principles set out in the Wessely review: choice and autonomy, least restriction, therapeutic benefit, and treating the person as an individual.
The main changes are:
- A higher threshold for detention under sections 2 and 3, framed around serious harm.
- Statutory Care and Treatment Plans for detained patients.
- Advance Choice Documents, allowing people to record treatment preferences while well.
- A nominated person chosen by the patient, replacing the nearest relative selected by statutory hierarchy.
- Limits on detaining people with a learning disability or autism under section 3 in the absence of a co-occurring mental disorder.
Implementation is phased over several years. A revised Code of Practice is expected to go to consultation from 2026, with substantive changes from 2027 onwards and some elements taking considerably longer. Until each provision commences, the 1983 Act as previously amended continues to apply. Check the current position before relying on any of it.
Documenting around an assessment
If your role is to record rather than to decide, four things make your note valuable.
- Describe rather than conclude. "Thought form showed flight of ideas and he was difficult to follow at several points" is more useful than "he was floridly manic", because the professionals making the statutory decision can weigh it themselves.
- Attribute every account. Police report, family report, the person's own account. Never merge them.
- Record disagreement explicitly. Where the person disputes what others describe, that belongs in the note in their words.
- Do not recommend a section. Unless you hold the relevant statutory role, that recommendation is not yours to make, and a note containing one is unhelpful at best.
No documentation tool should suggest a section, and any that does has misunderstood what it is for. Detention is a legal act reserved to specified professionals following a face-to-face assessment. A tool that produces a recommendation is making a clinical and legal decision it has no standing to make.
Scotland, Northern Ireland and Ireland
The framework described above applies to England and Wales only. The neighbouring jurisdictions differ materially, and assuming otherwise causes real problems.
Scotland operates under the Mental Health (Care and Treatment) (Scotland) Act 2003. The equivalent professional is the Mental Health Officer, and longer-term detention requires approval by the Mental Health Tribunal for Scotland rather than being a purely clinical decision.
Northern Ireland has the Mental Health (Northern Ireland) Order 1986, alongside the Mental Capacity Act (Northern Ireland) 2016 which introduced a fused framework unique in these islands.
Ireland operates under the Mental Health Act 2001, with Approved Centres and Mental Health Tribunals, and reform through the Mental Health Bill 2024.
If you move between jurisdictions, the terminology transfers poorly and the powers do not transfer at all.
Common questions
Who can carry out a Mental Health Act assessment in England and Wales?
Admission under sections 2 or 3 requires an application by an Approved Mental Health Professional together with two medical recommendations, at least one from a doctor approved under section 12 of the Act. A doctor cannot be an AMHP. Wherever practicable one doctor should have previous acquaintance with the person.
What is the difference between section 2 and section 3?
Section 2 is admission for assessment, lasting up to 28 days and not renewable, used where the diagnosis or appropriate treatment is not yet established. Section 3 is admission for treatment, lasting up to six months and renewable, used where the condition is already known and the treatment is identified.
How long can someone be held under section 136?
Up to 24 hours from arrival at the place of safety, extendable by up to a further 12 hours where a doctor certifies that assessment could not be completed within the original period. Since the Policing and Crime Act 2017 a police station may only be used for an adult in exceptional circumstances and never for anyone under 18.
What does the Mental Health Act 2025 change?
It amends rather than replaces the 1983 Act. The main changes are a higher threshold for detention, statutory Care and Treatment Plans, Advance Choice Documents, a patient-chosen nominated person replacing the nearest relative, and limits on detaining people with a learning disability or autism under section 3. Implementation is phased over several years from 2027.
Can a documentation tool recommend which section applies?
No, and none should. Detention is a statutory act reserved to specified professionals following a face-to-face assessment and multi-professional agreement. Software that recommends a section is making a clinical and legal decision it has no standing to make, and would almost certainly be a regulated medical device.