Enforcement time limits: the move to ten years explained

In England the time limit for taking enforcement action against a breach of planning control is now ten years for every category of breach. Section 115 of the Levelling-up and Regeneration Act 2023 amended section 171B of the Town and Country Planning Act 1990 to remove the four year rule, and the change took effect in April 2024. Breaches that had already become immune under the old four year rule before that date keep their immunity; breaches occurring afterwards need ten years.

The position stated here is as at September 2026. Enforcement provisions in the 2023 Act have been brought into force in stages, so verify the current wording of section 171B on the legislation site before relying on it for a specific case.

The four and ten year rules before the change

Under the old section 171B two periods applied, and working out which one you were in mattered a great deal.

The four year rule covered operational development, meaning building, engineering, mining or other operations, running from the date the operations were substantially completed. It also covered a change of use of any building to use as a single dwellinghouse, running from the date of the breach.

The ten year rule covered everything else: other changes of use, and breaches of condition or limitation. So an unauthorised extension became immune after four years, while an unauthorised office-to-flats conversion producing several units needed ten, and a breach of a condition restricting opening hours needed ten.

That split produced a well-known asymmetry. It rewarded the householder who built and waited, and it encouraged arguments about whether a conversion produced one dwelling or several. The four and ten year framework and the arguments it generated are set out in immunity from enforcement: the four and ten year rules.

What the Levelling-up and Regeneration Act 2023 altered

Section 115 of the 2023 Act rewrites section 171B so that a single ten year period applies in England to all breaches of planning control. The distinction between operational development, change of use to a single dwellinghouse and everything else disappears for the purposes of the time limit.

Everything else about enforcement stays as it was. The period still runs from substantial completion for operations and from the date the breach occurred for a change of use. Breach of condition still runs from the breach. And the discretion of the authority to take action, or not, is untouched: immunity is a defence, not an entitlement to act unlawfully in the meantime.

Wales did not make this change. A Welsh site retains the four and ten year framework, so guidance written for one nation does not transfer.

Which breaches the new period applies to

The change applies to breaches occurring on or after the date it took effect in April 2024. For operational development that means development substantially completed on or after that date. For a change of use to a single dwellinghouse it means the change occurring on or after that date.

Where the breach predates that date, the old period continues to apply to it. That transitional treatment is the part most often misread, and it produces three practical situations.

1. Operations substantially completed before that date, with four years already elapsed by then: immune, and the change makes no difference.
2. Operations substantially completed before that date, with less than four years elapsed: the four year period continues to run to its original end date.
3. Operations substantially completed on or after that date: ten years.

The date of substantial completion therefore carries much more weight than it used to, and on a disputed case it is the fact most worth evidencing precisely.

Deliberate concealment and enforcement orders

None of the time limits help where a breach has been deliberately concealed. Sections 171BA to 171BC allow a local planning authority to apply to a magistrates' court for a planning enforcement order, which reopens the enforcement window for a period after the concealment comes to light.

The authority has to show the apparent breach and that it was deliberately concealed, and it has to apply within six months of having sufficient evidence. The provision exists because of cases where a building was constructed behind hay bales or occupied without any external sign of the use.

Concealment does not mean simply failing to tell the council. It means positive steps to hide the breach. But the line between the two is fact-sensitive, and an applicant relying on a long period of undetected use should expect the question.

Evidence needed to establish immunity

The burden of proof sits on the person claiming immunity, on the balance of probabilities, and the evidence has to cover the whole period without a gap.

• Sworn statutory declarations from the occupier and from independent witnesses such as neighbours, tradespeople or a delivery firm.
• Council tax records and the valuation banding history, which are particularly strong for residential use.
• Utility accounts showing continuous supply to the unit in question.
• Dated photographs with metadata, and dated aerial imagery.
• Tenancy agreements, rent books and bank records showing rent received.
• Electoral roll entries and registration with a GP or a school.

A gap in the evidence is what defeats most of these cases. A use that ceased for a period and then resumed starts the clock again, so a claim resting on a run of documents with an unexplained two year hole in it will fail.

Contradictory evidence sinks claims as well. If the council holds a letter from the applicant asking about planning permission for the very use now said to have been running for a decade, that letter will appear in the officer report.

Lawful development certificates after the change

A certificate of lawfulness for an existing use or development under section 191 of the 1990 Act is the formal route to confirm that a breach has become immune. It is determined on evidence and law, not on planning merits, so the council cannot refuse one because it dislikes the development.

Apply for one before selling, refinancing or building on top of the immune development. A buyer's solicitor will not accept a statutory declaration in place of a certificate, and a lender is unlikely to either.

The change of period matters here in a specific way. Anyone who has been counting to four on operational development completed after April 2024 now has to count to ten, and applications submitted on the old assumption will be refused. Check the completion date first, then the evidence, then apply. Where the works were carried out under a permitted development right rather than in breach, the question is different again, as permitted development for larger rear extensions explains.

Checking the position for a specific breach

Work through four questions in order. What exactly is the breach: operations, a change of use, or a breach of condition? When did it occur or reach substantial completion? Which time limit applies given that date? And can the evidence cover the whole period continuously?

Listed building works sit outside all of this. There is no time limit on enforcement for unauthorised works to a listed building, and there is no route to immunity through the passage of time, however long ago the works were carried out.

Reform in this area has come in stages, and further enforcement provisions of the 2023 Act may be brought into force later. Follow developments on the planning law updates timeline and confirm the current text of the legislation before acting.

This is general guidance, not legal advice; check the position with your local planning authority or a qualified professional before relying on it.

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