Letting an annexe separately: the condition and the breach

Letting an annexe to a tenant who has no connection to the main house is almost always a breach of planning control. The permission for the annexe will carry a condition restricting its use to purposes ancillary to the main dwelling, and a separate letting is the clearest possible breach of it.

That is true whether or not the Valuation Office has given the annexe its own council tax band. The two systems are unconnected, and a separate band is evidence a council can use against you rather than a permission it has granted.

Ancillary use versus a separate planning unit

Planning law asks whether the annexe forms part of a single planning unit with the house, or whether it has become a planning unit of its own. The courts approach that by looking at the unit of occupation and at whether activities within it are ancillary to the primary use.

Physical and functional independence both matter, and functional independence usually decides it.

Physical indicators: a separate entrance, its own kitchen and bathroom, an enclosed curtilage, separate parking, its own utility supplies, a distinct postal address.

Functional indicators: whether the occupant shares facilities, meals, laundry, garden or access with the main household. Whether the occupant is a member of that household or a dependent relative. Whether the annexe could be occupied by a stranger without any interaction with the house.

A granny annexe with its own kitchen and shower can still be ancillary where the occupant is part of the household. The same building let on an assured shorthold tenancy to an unrelated tenant is a separate dwelling in all but name, whatever the drawings said.

The condition councils attach

The standard wording restricts occupation to purposes incidental or ancillary to the enjoyment of the main dwellinghouse, and prohibits the annexe being occupied as a separate dwelling or being let, sold or otherwise disposed of separately.

Some authorities go further and tie occupation to a named relationship, such as a dependent relative of the occupiers of the main house, or to a person employed on the holding in a rural case. Those are more restrictive and harder to live with.

Read the condition before assuming what it says. The three variants behave differently:

• ancillary use only, with no restriction on who occupies it
• occupation limited to a family member or dependent relative
• a requirement that the annexe be removed or reintegrated when the qualifying occupation ends

Also check whether the permission removed permitted development rights for the annexe, whether the curtilage was defined on the approved plan, and whether the annexe was consented as an extension rather than as a separate building. Those details determine what your options are later.

Evidence councils use to show separate occupation

Enforcement teams do not need to prove much, and the evidence is usually easy to assemble.

Council tax records showing a separate band. A tenancy agreement or a listing on a letting platform. Separate utility accounts. The electoral register. A separate postal address or a numbered door. Physical separation such as new fencing dividing the garden or a blocked internal connection. Neighbour statements about who lives there and for how long.

Occupiers sometimes volunteer the evidence themselves by applying for a separate council tax band to reduce a bill, or by registering a business address.

The council may serve a planning contravention notice requiring information about the use of the land, and there are penalties for failing to reply or for giving false information. Answer it accurately, and take advice before you do.

Enforcement, time limits and immunity

A breach of condition can be enforced through a breach of condition notice or an enforcement notice, and the two routes differ in appeal rights. A breach of condition notice carries no appeal to the Planning Inspectorate.

Time limits for immunity are in flux. The Levelling-up and Regeneration Act 2023 moves enforcement time limits in England to ten years, replacing the four-year period that previously applied to unauthorised dwellings. Commencement and the treatment of breaches that began before the change need checking for your specific facts and dates, as the answer turns on when the breach started.

Do not rely on a rule of thumb here. Immunity arguments depend on continuous use over the whole period, and the burden of proving it falls on the person claiming it. Gaps in occupation, periods when the annexe was used by family, or a change in the nature of the letting all break continuity.

Where a use has in fact become immune, the formal route to certainty is an application for a certificate of lawful existing use or development, supported by dated evidence such as tenancy agreements, bank statements, council tax records and utility bills covering every year of the period.

Applying to remove the ancillary condition

The route is a section 73 application to vary or remove the condition. It is determined as a planning application, so the council assesses whether an independent dwelling in that position is acceptable on its merits.

The issues that decide it:

1. whether a separate dwelling is acceptable in principle at that location, which is the hard test in the Green Belt, in open countryside and in areas with settlement boundaries
2. whether the annexe meets space standards and has adequate light, outlook and privacy as an independent home
3. whether the curtilage can be subdivided to give each dwelling usable private amenity space
4. parking provision for two households and whether the access can take it
5. amenity effects on neighbours from an intensified use
6. refuse storage, bin presentation and, on some sites, biodiversity or drainage requirements

Set the case out properly in a planning statement that addresses the location principle first, since that is where these applications fail. Check the authority's local validation list as well, because creating an additional dwelling often triggers requirements that an annexe application did not.

Illustrative example: a detached annexe in a large garden within a settlement boundary, built under a permission with an ancillary occupation condition. The owner applies under section 73 to remove the condition, provides a subdivided curtilage plan with 60 square metres of private garden for the annexe, two parking spaces per dwelling and a bin store at the frontage. The council grants permission subject to a condition removing permitted development rights for further extensions. The details are illustrative.

Council tax banding and why it is not planning evidence

The Valuation Office bands a self-contained unit separately for council tax under separate legislation. That decision says nothing about whether the planning use is lawful, and a council tax bill is not a defence to an enforcement notice.

The relationship runs the other way. Applying for a separate band is one of the most common triggers for a planning enforcement enquiry, because the two departments share data.

Note the reliefs that exist for an annexe in ancillary use. A discount applies where an annexe is occupied by a family member, and an exemption applies where it is occupied by a qualifying dependent relative. Both reliefs sit comfortably with ancillary planning use. Letting the annexe commercially removes both the relief and the planning argument at the same time.

There is a further trap on new build. Where a CIL annexe exemption was claimed, letting or disposing of the annexe separately within the disqualifying period can bring the levy back into charge, so check what was submitted and when. The CIL notice forms and their timing are unforgiving.

Options if the annexe is already let

Four routes, in ascending order of risk.

Revert to ancillary use, document the change, and keep the annexe available to the main household. Apply under section 73 to remove the condition and regularise the use. Apply for a certificate of lawfulness if the use is immune and you can evidence it year by year. Or wait for the council to act, which forfeits the chance to shape the outcome.

The first two are the ones that protect the value of the property. The last one tends to arrive as a letter about the tenant you have already housed.

This is general guidance, not legal advice. Check the position with your local planning authority or a qualified professional before relying on it. PlanScope provides AI-assisted draft reports for planning applications. Reports should be reviewed before submission. We do not guarantee planning approval. Enter your postcode on PlanScope to see which documents an application to regularise an annexe is likely to need.