Enforcement time limits for permitted development breaches

If you built something beyond permitted development limits and the council never noticed, the clock matters more than the merits. Immunity from enforcement runs from the date the breach happened, not from the date anyone complained, and once it has run the council loses the power to serve an enforcement notice on that breach.

For breaches in England the period is now ten years for everything. It used to be four years for building work and for converting a building into a single house, and that older four-year rule still applies to breaches that occurred before the change took effect. Which rule applies to your extension depends on when it was substantially completed.

The time limits and what starts them

Section 171B of the Town and Country Planning Act 1990 sets the periods. In its original form it gave four years for operational development, four years for the change of use of a building to use as a single dwellinghouse, and ten years for everything else, including other changes of use and breaches of condition.

Section 115 of the Levelling-up and Regeneration Act 2023 replaced that split in England with a single ten-year period. It was brought into force in England in April 2024, and the four-year periods were preserved for breaches that had already occurred. Check the date in the regulations that brought the section into force before you rely on it, because the cut-off decides whole cases.

The starting point differs by breach type. Operational development runs from substantial completion. A change of use runs from the date the material change occurred. A breach of condition runs from the date the condition was first breached, which for an ongoing breach is a rolling question rather than a single date.

Where the works themselves were close to the line, the 200 millimetre projection limit for solar panels is a good example of how small a margin can be enough to put an installation outside permitted development in the first place.

Substantial completion and how it is judged

For building work, the period starts when the operations are substantially complete. That is a question of fact and the courts take a broad view of it.

The leading authority is the House of Lords decision in Sage, which held that building operations should be looked at as a whole. A structure left without internal fit-out, where the original design intended a habitable building, may not be substantially complete even though it looks finished from the road. So a barn shell erected in one year and fitted out four years later can have a completion date much later than the owner assumes.

This cuts both ways for householders. A rear extension finished, decorated and occupied is straightforward. A garden building left as a shell, with the electrics run in two years afterwards, is not.

Keep the evidence of completion at the time. Nobody photographs the final render coat thinking about a certificate application a decade later, and that is exactly the photograph you will want.

Concealment and the loss of immunity

Immunity is not automatic. Where a breach has been deliberately concealed, two separate mechanisms can defeat it.

The first comes from the Supreme Court decision in Welwyn Hatfield, which concerned a dwelling built inside what appeared from outside to be a hay barn. The court held that positive deception could prevent an owner relying on the statutory time limit. The principle is narrow and turns on dishonesty rather than on mere failure to tell the council.

The second is the planning enforcement order. Sections 171BA to 171BC of the 1990 Act, inserted by the Localism Act 2011, let a local planning authority apply to a magistrates' court for an order allowing enforcement action outside the normal period where the breach has been deliberately concealed. The authority has to apply within six months of having sufficient evidence.

Neither applies to an ordinary case where the owner simply built the thing and said nothing. Not telling the council is not concealment.

Evidence needed to establish the period

The burden sits on the applicant, and the standard is the balance of probabilities. Clear evidence from the applicant, uncontradicted by anything the council holds, can be enough on its own.

What persuades case officers, roughly in order of weight:

• Dated aerial or satellite imagery showing the structure in place.
• Council tax records, utility accounts and electoral roll entries for a converted unit.
• Invoices, delivery notes and building contracts with dates.
• Statutory declarations from the owner, neighbours, the builder or a former tenant.
• Tenancy agreements, insurance schedules and mortgage valuations that describe the property as built.

Photographs need a provable date. Metadata from a phone helps. A photograph of the extension with a dated newspaper is old-fashioned and still works.

Gaps are the usual problem. A ten-year period needs evidence across the whole period, not just at the start and the end, because an interruption in use resets a change-of-use claim. For a house converted into flats, a void year with no tenancy and no council tax band is the sort of gap that loses cases.

Certificates of lawfulness for existing development

A certificate under section 191 of the 1990 Act is the formal confirmation that an existing building, use or breach of condition is lawful. Section 192 covers proposed works instead.

The application goes to the local planning authority on the standard form with a fee, a location plan, drawings of what exists and the evidence bundle. The council cannot consider planning merits. It is a legal and factual test only, so an ugly extension and an elegant one are treated identically.

Refusals mostly turn on thin evidence rather than on law. Where the council disputes the date, an appeal under section 195 goes to the Planning Inspectorate, and the inspector will weigh the statutory declarations against whatever the council's records show.

A short Planning Statement setting out the chronology, the statutory test and how each piece of evidence supports the claimed date makes the officer's job easier. That is worth doing even though planning merits are irrelevant, because a clear narrative reduces the chance of a refusal for insufficient information.

Why immunity is not the same as permission

Immunity stops enforcement of that breach. It does not grant planning permission, and four practical limits follow.

Building Regulations enforcement runs on its own timetable and an injunction is available without a long-stop date. Works to a listed building are outside the section 171B regime altogether, so there is no immunity period for unauthorised alterations to a listed building. Restrictive covenants and party wall liabilities are unaffected by anything the planning system does. And a later application affecting the same structure will be assessed against the lawful position, so an unlawful extension counted as part of the original dwelling can reduce what remains available under permitted development.

A certificate also has real value on sale. Conveyancers ask, indemnity insurance is more expensive than a certificate, and buyers' solicitors increasingly refuse to accept a statutory declaration alone.

Where the underlying question is whether the use itself ever changed, for instance in the move between C3 and C4 in an Article 4 area, the date of the material change of use is the fact everything else hangs on.

This is general guidance, not legal advice; check the position with your local planning authority or a qualified professional before relying on it. A lawful development certificate is the only formal way to confirm that works are lawful.

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