Landlords conflate two different questions. Is it an HMO? and does it need a licence? are not the same, and the first one is where the duties come from.
A property can be an HMO with no licence required anywhere in the country — and the management regulations still bind you, the fire safety duties still bind you, and breaching them is still an offence.
The standard test — section 254(2)
A building or part of a building is an HMO under the standard test if all of these are true:
- It consists of one or more units of living accommodation not consisting of a self-contained flat.
- The living accommodation is occupied by persons who do not form a single household.
- It is occupied by those persons as their only or main residence.
- Their occupation is the sole use of that accommodation.
- Rents are payable or other consideration is provided.
- Two or more of the households share one or more basic amenities, or the accommodation lacks them.
Basic amenities are a toilet, personal washing facilities, or facilities for cooking. One shared kitchen is enough. It does not take a shared bathroom as well.
What a "household" actually means — section 258
This is the part that decides most cases, and the definition is narrower than people expect. Persons form a single household if they are all members of the same family:
- married, civil partners, or living together as if they were;
- relatives — parent, grandparent, child, grandchild, sibling, uncle, aunt, nephew, niece, cousin;
- step-relations and half-blood relations count as full.
Everything else is a separate household. Friends are not a household. Colleagues are not a household. Three unrelated professionals sharing a flat are three households, and the property is an HMO.
The threshold that surprises people
Three occupiers from two or more households sharing an amenity is an HMO. Not five. Five is the mandatory licensing threshold, which is a different question entirely.
So a two-bedroom flat let to a couple and their friend: the couple are one household, the friend is another, three people, shared kitchen. HMO.
The other two tests
Section 254 has three routes in, and the standard test is only the first.
The self-contained flat test — s.254(3)
A self-contained flat can itself be an HMO, where the same conditions are met inside it. A three-bed flat sharing a kitchen between unrelated occupiers qualifies even though the flat has its own front door and facilities.
The converted building test — s.254(4), and s.257
A building converted into non-self-contained units. And separately, section 257 catches buildings converted into self-contained flats where the conversion did not meet the 1991 Building Regulations and fewer than two-thirds are owner-occupied. That one catches freeholders who do not believe they are HMO landlords at all.
What is excluded
Schedule 14 of the Act takes some buildings out: those managed by public bodies or registered providers, student halls managed under an approved code, buildings occupied by religious communities, owner-occupied buildings with no more than two lodgers, and buildings where the occupation is by a resident landlord within limits.
Why the definition matters even without a licence
The moment a property meets the definition:
- the management regulations apply, licensed or not — and breaching them is an offence under section 234(3);
- the council can serve improvement notices against HMO-specific hazards;
- an additional licensing designation, if your council has one, catches you at three occupiers rather than five — see additional licensing and the three-tenant question;
- your insurance and your mortgage terms very likely say something about it.
England and Wales
Section 254 is the same in both — the Housing Act 2004 extends to England and Wales and the definition was never devolved. Mandatory licensing thresholds diverge, and Wales adds Rent Smart Wales on top. See HMO licensing in Wales and the divergence map.
Try the tool. If it is an HMO and it is licensed, room sizes are a mandatory licence condition rather than a preference. The room size checker measures each bedroom against them, with the regulation cited on every verdict.
Information tool, not legal advice.
Common questions
What counts as an HMO?
Under section 254 of the Housing Act 2004, broadly: living accommodation occupied by people from two or more separate households, as their only or main residence, paying rent, sharing a toilet, washing facilities or cooking facilities. Three unrelated sharers with one kitchen is an HMO — the five-person figure people quote is the mandatory licensing threshold, not the definition.
What is a household for HMO purposes?
Section 258 defines it as members of the same family — married or civil partners or living as such, and relatives including parents, grandparents, children, grandchildren, siblings, uncles, aunts, nephews, nieces and cousins, with step and half-blood relations counting as full. Friends and colleagues are separate households, however long they have lived together.
Is a property an HMO if it does not need a licence?
Yes, and this is the distinction that matters. Meeting the section 254 definition brings the management regulations, HMO-specific hazard enforcement and often insurance and mortgage conditions, whether or not any licence is required. Breaching the management regulations is an offence in its own right.
Is a couple plus one friend an HMO?
Yes, if they share a basic amenity. The couple are one household and the friend is a second, giving three occupiers in two households — enough for the standard test.