Planning Enforcement in London: What Happens If You Build Without Permission

What counts as a breach of planning control?

A breach of planning control is defined in section 171A of the Town and Country Planning Act 1990 as either carrying out development without the planning permission it required, or failing to comply with a condition or limitation attached to a permission. In practice that covers two situations most London homeowners meet: building something that needed permission and never got it, and breaching a condition on a permission you did receive — for example ignoring an obscure-glazing condition, an approved-materials condition, or a restriction on hours of use.

Importantly, a breach is not in itself a crime. Building without permission is a civil planning matter, and a council must decide whether it is expedient to act. That word matters. Officers weigh the harm caused against the planning merits, and they will frequently invite you to apply for permission rather than jump straight to formal action. The offence only arises later, if you ignore a notice that has taken effect.

What enforcement powers does a London council have?

A council has a graded toolkit, and it chooses the tool to fit the harm. It rarely reaches for the heaviest option first. Understanding each notice — what it does, how long you have to respond, and what happens if you ignore it — is the single most useful thing a homeowner can know when a letter arrives from the planning enforcement team.

How long does a council have to take enforcement action?

Since 25 April 2024, England has a single time limit of 10 years for taking enforcement action against almost every breach of planning control. This was introduced by the Levelling-up and Regeneration Act 2023 and it swept away the old split system. Previously, operational building works and the change of use of a building to a single dwellinghouse became immune after just 4 years, while other changes of use and breaches of condition had 10 years.

The reform matters most to anyone relying on the passage of time to make an unauthorised extension lawful. A rear extension built without permission, which under the old rule would have become immune four years after completion, now needs a full ten years. Breaches that were already immune before the 2024 change generally keep that immunity, so the exact completion date of the works can be decisive. If your project sits near either threshold, take advice before assuming it is safe.

How do you appeal an enforcement notice?

If you receive an Enforcement Notice you can appeal to the Planning Inspectorate, and you must do so before the date the notice is due to take effect — the effective date stated on the notice, at least 28 days after it was served. Miss that deadline and the right is lost; the notice bites and the courts will not extend the time. The appeal is made on one or more of the grounds set out in section 174 of the Act.

The grounds range from arguing that planning permission ought to be granted for what was done (ground a, which is treated as a retrospective application and carries a fee), through disputing that a breach occurred at all, to arguing that the time limit for enforcement has already expired (ground d), or that the required steps or compliance period are excessive. Lodging the appeal suspends the notice until the Inspector decides, which is a key reason to act within the window rather than comply under protest.

• Ground (a) — planning permission should be granted; this doubles as a retrospective application
• Ground (b) — the matters alleged have not occurred as a matter of fact
• Ground (c) — the matters do not constitute a breach of planning control
• Ground (d) — enforcement is out of time because the breach is immune
• Grounds (e)-(g) — the notice was not properly served, the steps go beyond what is needed, or the compliance period is too short

What is the difference between enforcement and prosecution?

Enforcement and prosecution are two different stages, and confusing them causes needless panic. Enforcement is the civil process of requiring a breach to be put right through the notices described above. Serving an Enforcement Notice, on its own, is not a criminal charge and does not give you a criminal record. It is the planning system asking you to remedy something.

Prosecution comes later and only if you ignore a notice that has taken effect. Failing to comply with an Enforcement Notice is a criminal offence under section 179, carrying an unlimited fine in the Crown Court, and the court can take account of any financial benefit you gained. Two categories are different from the outset, though: unauthorised works to a listed building, and certain works in a conservation area such as demolition or felling protected trees, are criminal offences from the moment they are carried out, with no need for a notice first.

How do you regularise unauthorised work?

There are two routes back to legality, and which one fits depends on how old the work is. If the breach is recent, the answer is usually a retrospective planning application — the same householder application you would have made beforehand, judged on the same policies, simply submitted after the event. A council cannot refuse to consider it, and a well-prepared submission with accurate existing and proposed drawings is exactly what turns an enforcement risk into an approval. Getting the drawings right is what stands between a retrospective application that succeeds and one that invites the very notice you are trying to avoid.

If the work is old enough to have passed the ten-year limit, the route is a Lawful Development Certificate under section 191, which formally confirms the development is immune from enforcement and therefore lawful. It is evidence-based: you must prove, on the balance of probabilities, the date the works were completed and that they have continued since, using dated photographs, invoices, utility records and sworn statements. Either route needs a clean, credible drawing set, and choosing the wrong route wastes both time and the application fee.

Why is London enforcement stricter than elsewhere?

London boroughs tend to enforce more actively than rural districts for practical reasons: dense terraced streets mean neighbours notice and report unauthorised work quickly, land values make rule-breaking tempting, and most boroughs run dedicated, well-staffed enforcement teams. Add the capital's extensive coverage of conservation areas and Article 4 directions — which remove permitted-development rights borough by borough — and work that would be lawful elsewhere can require permission here.

The stakes rise sharply with heritage. London has a very high concentration of listed buildings and conservation areas, and unauthorised alterations to a listed building are a criminal offence with no time limit and no need for a prior notice. Before assuming any project is permitted development, a London homeowner should check the borough's local plan, any Article 4 direction, and whether the property is listed or in a conservation area.