The ten year enforcement limit and what it covers

England now has a single ten year enforcement time limit for almost every planning breach. The old four year rule, which gave operational development and the change of use of a building to a single dwellinghouse immunity after four years, has gone for breaches that happened on or after 25 April 2024. For landlords and investors who bought on the basis that an unauthorised conversion would become immune in four years, the arithmetic has changed. This explainer is current as at 9 October 2026, and the commencement position should be confirmed on legislation.gov.uk before you rely on it.

What the limits used to be

Section 171B of the Town and Country Planning Act 1990 has always set the clock. Before the change it ran three different periods.

Four years for operational development, running from the date the building, engineering, mining or other operations were substantially completed. Four years for a change of use of a building to use as a single dwellinghouse, running from the date of the breach. Ten years for any other breach, which covered all other changes of use and the breach of a condition or limitation.

That split created the pattern everyone in the sector knew. A rear extension built without permission was beyond enforcement after four years. An office converted to flats without permission took ten, because it was a change of use to multiple dwellings rather than to a single one. A single flat carved out of a house took four.

The change Part 3 of the 2023 Act makes

Part 3 of the Levelling-up and Regeneration Act 2023 amended section 171B so that the time limit for taking enforcement action in England is ten years in every case. The four year periods were removed rather than extended in stages.

The amendment applies in England only. Wales retains the earlier structure, so a Welsh property is assessed under the four and ten year periods and anyone advising across the border needs to check which regime applies, with Planning Policy Wales as the policy context.

Nothing else about enforcement changed with it. The council still has a discretion whether to act, the expediency test still applies, and the remedies, enforcement notices, breach of condition notices, stop notices and injunctions, are unchanged.

Which breaches the ten year limit now covers

Two things sit outside the regime entirely and are worth stating plainly, because owners assume otherwise. Unauthorised works to a listed building never become immune through the passage of time, and carrying them out is a criminal offence under the Planning (Listed Buildings and Conservation Areas) Act 1990. Works in breach of a Tree Preservation Order are likewise an offence rather than a matter of immunity.

Works completed before the change

The transitional position is the part that gets misread. The old four year limits continue to apply to breaches that occurred before 25 April 2024, so immunity already accrued or already running on that date is not reopened.

Read that carefully. A single flat created in 2021 was already within four years of the breach on 25 April 2024, so it reached immunity in 2025 under the old limit. A flat created in May 2024 will not be immune until 2034.

The practical consequence for anyone buying converted stock is that the date of the breach, not the date of purchase or the date of discovery, decides which regime applies. Where the evidence puts the date close to April 2024, the difference between the two answers is six years of exposure.

Proving the date works were substantially completed

Immunity is a matter of evidence and the burden falls on the owner. Substantial completion is judged on the building as a whole, not on the last cosmetic item, and a scheme left unfinished to delay the clock does not start it.

What persuades an officer or an inspector:

1. Dated invoices from builders, scaffolders, skip hire and material suppliers, ideally with the site address on them.
2. Bank statements or card records matching those invoices, which are much harder to challenge than the invoices alone.
3. Council tax records, utility accounts, tenancy agreements and electoral roll entries for a new unit, each showing a start date.
4. Dated photographs with metadata intact, and aerial imagery where the date of capture is published.
5. A statutory declaration from the owner, and ideally from the builder, setting out the sequence with dates.
6. Building control records or a completion certificate, if one was sought.

Patchy evidence is the normal reason these cases fail. One invoice and a recollection will not carry a ten year period, and the longer period means the paperwork has to survive longer, which is a genuine problem now rather than a theoretical one. Keep the file with the deeds. The permitted development limits that might have covered the works in the first place are worth checking too, as our note on air source heat pumps and permitted development limits shows for one small class.

Effect on certificates of lawfulness

A certificate under section 191 of the 1990 Act is how immunity is turned into something a lender or buyer will accept. The test the council applies is whether, on the balance of probabilities, the use or works have become immune from enforcement, which means the applicant must now show ten years of continuous unauthorised use or ten years since substantial completion.

For continuing uses, the ten years must be unbroken and run up to the date of the application. A gap, a period of genuine vacancy, or a reversion to the lawful use resets it.

Councils are entitled to refuse where the evidence is thin and to grant a certificate in narrower terms than were applied for. Both happen. If you are applying on the strength of an old conversion, decide before you submit whether the weakest link in the chain of evidence will hold, because a refusal is a public record that a purchaser's solicitor will find.

What this means when you buy or sell

Indemnity insurance against enforcement action usually prices on the remaining exposure period. A longer limit means a longer exposure, and insurers have adjusted accordingly, so the cost and the availability of cover for recent unauthorised works are not what they were.

For sellers the sequence is unchanged but the timing is slower. Establish the date of the breach, assemble the evidence while the people who did the work are still contactable, and apply for the certificate before marketing rather than during a transaction.

For buyers the question to put to a seller is specific. Not "is this lawful" but "on what date was this substantially completed, and what documents prove it".

Reform news on enforcement and the rest of the 2023 Act is tracked on the UK planning law timeline, and the plan-making changes running alongside it are covered in our piece on plan making reform and emerging plans.

If the answer is that an application is needed after all, enter your postcode on PlanScope to see which reports the site is likely to need.

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.