The ten year rule for change of use immunity

The ten year rule change of use position is straightforward in principle and awkward in evidence. Under section 171B(3) of the Town and Country Planning Act 1990, a material change of use becomes immune from enforcement once it has subsisted continuously for ten years, which means the council can no longer serve an enforcement notice and the use becomes lawful. The difficulty is almost never the law. It is proving, to a council that has no records of the use, that it ran without a break for the whole decade and was still running on the day you applied.

Immunity is not permission. It makes an existing use lawful and it does nothing for any other consent regime you may have breached.

What the time limit applies to

Section 171B sets out separate periods for different breaches. A material change of use, and a breach of condition, has historically carried a ten year period. Building, engineering, mining or other operations carried a four year period, as did a change of use to a single dwellinghouse.

So the first question on any immunity claim is what the breach actually is. Converting a house into flats is a material change of use. Converting an outbuilding into a self-contained dwelling involves both operations and a change of use, and the two can fall on different timetables. Running a business from a domestic garage may be no breach at all if the use remains ancillary to the dwelling, which is a different argument entirely and one our note on ancillary use and the separate planning unit deals with.

The planning unit matters as much as the period. If the use you rely on occupied only part of a larger unit, you may be claiming immunity for something the council does not accept exists as a unit at all.

The ten year extension and when it bites

Section 115 of the Levelling-up and Regeneration Act 2023 extends the four year periods in England to ten years, so all breaches move onto a single ten year clock. It came into force in April 2024 and applies to breaches which began on or after that date, which means a breach that began before that date keeps the four year period.

That transitional line is now the most commonly misunderstood point in the whole area. An unauthorised annexe first occupied in 2021 sits on the old four year rule for the building works. One first occupied in 2025 sits on ten years. Verify the commencement position and the current wording of section 171B on legislation.gov.uk before advising anyone, because commencement orders under the 2023 Act have been made in stages.

For a material change of use the practical effect is nil. It was ten years before and it is ten years now.

Continuity and why gaps defeat a claim

The use has to have subsisted continuously throughout the period, and it has to be subsisting at the date of the application or the enforcement action. The courts have consistently refused to let applicants aggregate separate periods, so an earlier decade of unauthorised use that stopped in 2014 cannot be revived by a fresh period beginning now.

Short interruptions are a question of fact and degree. A tenant leaving and a new tenant arriving three months later is normally continuity of use, because the character of the use of the land did not change. A building standing empty for two years while the owner decided what to do with it invites an argument that the use was abandoned, and abandonment is judged on the physical condition of the property, the period of non-use, whether there was any intervening use, and the owner's intentions.

Seasonal use is its own puzzle. A holiday let occupied for seven months a year can still be a continuous use in planning terms, because the use of the land is a holiday letting use all year round even when nobody is in the building. Explain it that way rather than apologising for the gaps.

Evidence that satisfies the test

The burden sits with the applicant, and the standard is the balance of probabilities. Where the applicant's evidence is precise and unchallenged by anything the council holds, it can be enough on its own. That is a real advantage, and it is lost the moment a statement turns out to be wrong on a date.

The evidence that carries weight, roughly in order:

1. Statutory declarations from people with direct knowledge, covering specific dates and what they personally saw or did, rather than general assertions about how long something has been there.
2. Council tax or business rates records, which have the advantage of being the council's own data.
3. Tenancy agreements, rent books and rent receipts running across the period.
4. Utility bills showing separate supplies or separate meters for separate units.
5. Accounts, VAT returns and trading records for a business use.
6. Dated photographs, aerial imagery and street-level imagery.
7. Electoral roll entries, insurance policies, licences such as an HMO licence, and correspondence addressed to the individual unit.

Aim for at least two independent strands covering every year. One document per year from one source leaves a gap the council will find. Our notes on proving an existing lawful use and on evidencing a lawful use where the history is silent go through the sequence in more detail.

Be honest about weak years. An application that flags a thin period and explains why is treated better than one that glosses over it and is caught.

Deliberate concealment and planning enforcement orders

Immunity is not available to someone who has deliberately concealed a breach. The Supreme Court held in Welwyn Hatfield Borough Council v Secretary of State for Communities and Local Government that positive deception designed to secure immunity defeats the claim, and Parliament then added sections 171BA to 171BC to the 1990 Act so councils can apply to a magistrates court for a planning enforcement order where a breach has been deliberately concealed. An order effectively restarts the clock.

What counts as concealment is dishonest conduct rather than ordinary silence. Not telling the council about a change of use is not concealment. Submitting a misleading application, building something behind a hoarding and denying its existence, or claiming a building is agricultural while living in it, is.

The practical lesson for anyone buying a property with an unauthorised use: ask what the vendor told the council and when. A concealment finding against a previous owner can follow the land.

Applying for a lawful development certificate

A certificate of lawful existing use or development under section 191 of the 1990 Act is the only formal way to confirm that a use is lawful. Everything else is opinion, including a solicitor's view and a planning consultant's view.

The application goes to the local planning authority on the standard form with a plan, a precise description of the use claimed, and the evidence. Get the description right, because the certificate is issued in the terms applied for and a certificate for the wrong thing is worth very little. Where you are describing a use that does not fall in a class under the Use Classes Order, describe the activity rather than reaching for a class label.

Fees are set nationally and a certificate for an existing use is charged at the rate that would apply to a planning application for the same development, with a proposed use certificate under section 192 charged at half that. Fees are indexed, so check the current schedule before you send the cheque. Refusal can be appealed to the Planning Inspectorate under section 195, and the appeal is determined on the evidence rather than on planning merits.

One tactical point. The council can refuse for want of evidence and you can reapply with better evidence, but every unsuccessful application is a document the council keeps. Assemble the pack properly the first time.

Assembling the evidence pack

Build it as a chronology. A single table with one row per year, columns for the evidence items relied on, and a short narrative for each change of occupier or activity. Attach the documents as numbered appendices and cross-reference them from the table.

Then add the declarations. Draft them so each person speaks only to what they know, name their role and their connection to the property, and date and witness them properly. A declaration that reads as though someone else wrote it in the same voice as three others is worth less than three short, distinct statements.

Finish with a short planning analysis: what the lawful use was before, what the material change of use was, when it occurred, why the period is continuous, and why the use subsists today. Where a Planning Statement is needed for a related application, the same chronology feeds straight into it.

PlanScope can draft the supporting statement and the chronology structure around the documents you hold, marking any gap in the record rather than filling it. This is general guidance rather than legal advice, so check the position with your local planning authority or a qualified professional before relying on it, and remember that a lawful development certificate is the only formal confirmation that a use is lawful.

PlanScope provides AI-assisted draft reports for planning applications. Reports should be reviewed before submission. We do not guarantee planning approval. Browse the report types to see what usually accompanies a certificate application.