Enforcement time limits for building works and immunity

Unauthorised building works in England become immune from enforcement ten years after they were substantially completed. The four-year rule that used to protect operational development was removed by section 115 of the Levelling-up and Regeneration Act 2023, which came into force in England on 25 April 2024. The enforcement time limit for building works therefore turns on one date, the date of substantial completion, and on whether the old four-year period had already run before the law changed. For a farm building, a stable block, a yard or an access track, that date is usually contested and almost never documented.

Immunity periods for operational development

Section 171B of the Town and Country Planning Act 1990 sets the periods. Before the 2023 Act, subsection (1) gave four years from substantial completion for building, engineering, mining or other operations carried out without permission. Subsection (2) gave four years for an unauthorised change of use to a single dwellinghouse. Everything else, including other changes of use and breaches of condition, sat under the ten-year period in subsection (3).

In England there is now one period of ten years for every kind of breach. The practical effect on a rural holding is uncomfortable. A general purpose building put up without permission in 2022 would once have been beyond reach by 2026. It will now be vulnerable until 2032.

Immunity is also narrower than owners assume. It stops enforcement under the 1990 Act. It does nothing about unauthorised works to a listed building, where there is no equivalent immunity period and the offence under the Planning (Listed Buildings and Conservation Areas) Act 1990 does not expire with time. Nor does it cure a breach of the Building Regulations or a breach of a restrictive covenant.

Substantial completion as the trigger

The clock starts when the building operations are substantially complete, not when they started and not when the building was first used. The House of Lords settled the approach in Sage v Secretary of State for the Environment, Transport and the Regions, holding that completion is judged against the building operation originally intended, taken as a whole.

That matters more than it sounds. A barn conversion left as a weathertight shell with no internal floors, no staircase and no services is not a substantially complete dwelling. The operations the owner set out to carry out have not finished, so no period has begun to run. Owners who leave a job deliberately unfinished in the hope of banking time usually achieve the opposite.

Engineering operations are read the same way. Regrading a field, laying a hardstanding or forming a track is complete when the physical works are finished, which is normally easier to date than a building because the plant hire and aggregate deliveries leave a paper trail.

What the 2023 Act changed and what it preserved

Section 115 of the Levelling-up and Regeneration Act 2023 substitutes a single ten-year period in section 171B for England. The amendment does not revive immunity that had already been earned. Where four years had fully run before that date, the development stayed immune, and the authority cannot reopen it by pointing at the new period. Check the regulations that brought the change into force, and their saving provisions, before relying on a date close to the boundary, because a building completed in the spring of 2020 sits very near the line.

Wales is a separate jurisdiction here. The four-year rule for operational development continues to apply in Wales under Welsh provisions, so an owner with land either side of the border can hold two buildings of the same age in two different legal positions. Anyone dealing with a Welsh site should take the position from Welsh legislation and guidance rather than the England position described here.

Evidence that fixes the completion date

The burden sits on the owner, on the balance of probabilities. Inspectors generally follow the approach in Gabbitas, that an applicant's own evidence can be accepted where the authority has nothing credible to contradict it. Nothing credible is the operative phrase. A bare assertion in a covering letter will not survive a contested case.

The evidence that carries weight is dull and dated:

• statutory declarations from the owner, and separately from the builder, groundworker or agricultural contractor who did the work
• invoices, delivery notes and bank statements for materials, concrete, steel and plant hire, with the dates legible
• dated photographs, with an explanation of who took them and on what device
• aerial photography, including the authority's own historic imagery and the national mapping record
• utility connection records, insurance schedules, business rates entries and agricultural land parcel records showing the building in place

Assemble it in a chronology rather than a bundle. Where an inspector has to reconcile three sources that point at three different years, the appeal usually fails on the standard of proof rather than on the law, and the reasoning in the decision letter will say so plainly. Reading a few decisions in this area is the fastest way to calibrate what an inspector accepts, and how a decision letter is structured tells you where the evidential findings sit.

Deliberate concealment and the planning enforcement order

Sections 171BA to 171BC, inserted by the Localism Act 2011 after the Supreme Court decision in Welwyn Hatfield Borough Council v Secretary of State for Communities and Local Government, let an authority apply to a magistrates' court for a planning enforcement order where an apparent breach has been deliberately concealed.

The application must be made within six months of the date on which evidence of the apparent breach came to the authority's knowledge, and the authority has to satisfy the court that concealment was deliberate. If the order is granted, the authority gets a further year in which to act, whatever the ordinary time limit says.

This is not aimed at the owner who simply never told anyone. It bites where the breach was actively hidden, for example a dwelling disguised as a hay barn, or a use screened behind a facade built to look agricultural.

Where only part of the works is immune

Each operation is judged on its own facts. A general purpose building completed in 2011 may be immune while a mezzanine floor, a roller shutter door or a lean-to added last year is a fresh operation with its own ten-year clock.

Authorities often issue one notice covering everything on a yard and require the whole lot to be removed. Where part of the works is immune, the notice over-reaches, and the answer is usually a combination of ground (d) on the immune elements and ground (f) on the steps required, arguing that removal of the whole exceeds what is needed to remedy the actual breach. Plans matter here. Mark up a measured site plan showing each structure, its footprint and its claimed completion date, because an inspector cannot vary a notice sensibly without knowing what to carve out.

Pleading ground (d) on an enforcement notice

Ground (d) in section 174(2) is that at the date the notice was issued, no enforcement action could then be taken in respect of any breach of planning control which may be constituted by the matters alleged. The test date is the date of issue of the notice. Time running on after that date does not help, which is why a notice served shortly before immunity would have been earned is so damaging.

The procedure is tight:

1. Appeal to the Planning Inspectorate before the date the notice takes effect, which will be at least 28 days after service. Miss it and the notice bites, with no route back.
2. State every ground you rely on, with a full statement of case and the supporting evidence.
3. Expect the authority to produce its own dating evidence, and keep your chronology open so it can answer theirs rather than repeat yours.

An enforcement appeal carries no fee, and lodging it suspends the notice until the appeal is decided. Where no notice has yet been issued, the cleaner route is an application under section 191 for a lawful development certificate for existing operations, which converts a factual argument into a formal confirmation and can be appealed under section 195 if refused. A certificate is the only way to put the question beyond doubt. Watch for the authority reframing its case once the evidence lands, a pattern worth understanding before you draft, and the way inspectors handle a shifting council position is instructive.

If you are putting in a retrospective application alongside, or instead of, an appeal, the supporting narrative does the heavy lifting, and a Planning Statement that sets out the planning history, the dates and the policy position is the document officers read first. PlanScope provides AI-assisted draft reports for planning applications. Reports should be reviewed before submission. We do not guarantee planning approval.

This is general guidance, not legal advice. Enforcement cases turn on their own facts and dates, so check the position with your local planning authority or a qualified professional before relying on it. Enter your postcode on PlanScope to see which reports a retrospective application on your site is likely to need.