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

The most common trigger for a planning enforcement investigation in London is a complaint from a neighbour. When a complaint is received, the local planning authority's enforcement team will typically carry out a desktop investigation (checking planning records, aerial photography, and the property history) before deciding whether to carry out a site visit. Not every complaint results in an investigation — the planning authority must assess whether a breach of planning control appears to have occurred and whether it would be expedient to take enforcement action. Other triggers for enforcement investigations include: planning officers identifying apparent breaches during site visits for other purposes; aerial photography updates (planning authorities periodically review aerial imagery to identify new structures); Building Control referrals (where Building Control identifies work that may also require planning permission); and traffic and highways officers identifying unlawful vehicle crossings or hardstanding. Once an investigation is opened, the planning authority has statutory powers to enter land and take photographs for the purposes of ascertaining whether a breach of planning control has occurred. They also have the power to issue a Planning Contravention Notice requiring information about the development.

Planning enforcement in England (and by extension London) is subject to time limits after which the local planning authority can no longer take enforcement action. These are: The 4-year rule: applies to operational development (buildings and structures, including extensions, outbuildings, and other construction) and to changes of use of a building to a dwelling house. The 4-year period runs from the date of substantial completion of the development. After 4 years from completion, the development is immune from enforcement action and the owner can apply for a Lawful Development Certificate (Existing Use) confirming this. Crucially, the 4-year clock starts from completion of the development, not from the date planning permission was or was not obtained — so a building that has stood for 4 years is generally immune regardless of whether permission was granted or not. The 10-year rule: applies to material changes of use (other than to a dwelling house) and to breaches of planning conditions. For example, using a building as a commercial premises without change of use permission for 10 years renders the use lawful. For breaches of conditions, the 10-year clock runs from the date of the breach. Important caveat: these time limits can be defeated by evidence of concealment — if the planning authority can show that the owner deliberately concealed the development to prevent discovery, the time limits may be extended. Where concealment is alleged, the planning authority will need to prove active steps were taken to hide the breach, not merely that it was not obvious.

The planning enforcement process typically proceeds in the following sequence: Stage 1 — Site investigation: The planning officer visits the site and assesses whether a breach of planning control has occurred. In straightforward cases, they may be able to determine immediately that: no breach occurred (the development is permitted development); the development is time-barred; the breach is de minimis and enforcement would not be expedient. Stage 2 — Planning Contravention Notice (PCN): If a breach appears to have occurred and further information is needed, the authority may issue a PCN to the owner or occupier. The PCN requires specific information to be provided within 21 days (for example, the date the development was completed, the purpose for which it is used, or whether planning permission was sought). Failing to respond to a PCN without reasonable excuse, or providing false information, is a criminal offence punishable by a fine. Stage 3 — Enforcement action decision: After gathering information, the planning authority decides whether to take formal enforcement action. Options include: issuing a formal enforcement notice; seeking an injunction (in serious cases); or taking no formal action but writing to the owner to record the breach and advise that action may be taken in future. Stage 4 — Enforcement Notice: An Enforcement Notice is a formal legal notice that identifies the breach, requires specific steps to remedy it within a specified time period (typically 28 days to several months depending on the complexity of the required works), and is registered as a local land charge (appearing on any future property searches). The owner has the right of appeal to the Planning Inspectorate within the period specified in the notice. Failure to comply with an Enforcement Notice is a criminal offence.

For the vast majority of residential planning enforcement cases in London — an extension built without permission, a roof alteration outside permitted development limits, an outbuilding that exceeds the permitted development size threshold — the most practical and cost-effective resolution is a retrospective planning application (formally known as an application for planning permission for development already carried out, under Section 73A of the Town and Country Planning Act 1990). A retrospective application is assessed on exactly the same policy basis as any other planning application: if the development would have been granted permission had the application been made in advance, it should be granted retrospectively. The fact that development has already been carried out does not in itself make it less likely to be approved (though it may irritate the planning officer). If permission is granted, the enforcement matter is resolved. If permission is refused, the enforcement notice will stand and the development must be removed or altered to comply. When considering whether to submit a retrospective application or appeal an enforcement notice, take professional advice from a planning consultant — the two routes have different merits depending on the specific development and the reasons for the enforcement notice.

Unresolved planning enforcement matters can significantly complicate the sale of a property. Standard conveyancing searches include a local land charge search, which will reveal any registered enforcement notices. Even where no enforcement notice has been issued, a buyer's solicitor may raise questions about works that are visible but do not have planning permission shown on the property's planning history. Options for managing planning enforcement risk on a property sale: Planning indemnity insurance — specialist insurance policies are available that indemnify the buyer (and their mortgage lender) against the risk of the local planning authority taking enforcement action in the future. These policies are available for development that is time-barred or where enforcement is unlikely to be pursued in practice. Premiums are typically a one-off payment based on the rebuild value of the affected structure. The insurer assesses the risk before offering terms. Regularisation before sale — obtaining a Lawful Development Certificate or a retrospective planning permission before selling removes the risk from the conveyancing process entirely and removes the need for indemnity insurance. This is generally the cleaner approach where the development is time-barred or where a retrospective application is likely to succeed.