Built Without Planning Permission? Retrospective Applications, Enforcement and Time Limits

It usually surfaces at the worst possible moment: a buyer’s surveyor flags an outbuilding that doesn’t appear on any historic planning record, or a mortgage valuer asks for evidence of consent for a rear extension that’s clearly been there a while, and suddenly a sale that was progressing smoothly stalls on a question nobody had thought to ask. Unauthorised development can create serious practical problems, but it isn’t automatically catastrophic — and the internet is full of confident, outdated advice about exactly when it stops being an enforcement risk. In England, that advice changed materially in 2024.

Before anything else: was permission actually required?

It’s worth establishing this properly before assuming the worst. A surprising amount of work that looks unauthorised on paper turns out not to be, because it fell within permitted development rights at the time it was carried out, because it received a permission that simply isn’t obvious from the current online record, because it was covered by an earlier consent that covers more than the current owner realises, or because it predates the planning controls now being considered.

Missing paperwork is not the same as an actual breach. It’s worth checking the council’s planning register and, where relevant, applying for a Lawful Development Certificate to establish the planning position formally before treating anything as a confirmed problem.

Retrospective applications

Where permission genuinely should have been sought and wasn’t, it is possible in England in many cases to submit a retrospective planning application under section 73A of the Town and Country Planning Act 1990 — essentially an application seeking permission for development that has already taken place.

The fact that the work already exists does not create a separate planning merits test. A retrospective application has to be considered in the normal way, and there is no entitlement to permission simply because money has already been spent. Equally, retrospective status is not supposed to operate as a punishment in itself.

If the development is acceptable in planning terms, the council may grant permission, potentially subject to conditions. If it isn’t acceptable, permission can be refused and enforcement action may follow.

There is an important complication once enforcement action is involved. Retrospective applications and enforcement appeals are not unlimited alternative chances to secure permission after the event. A council can in some circumstances decline to determine a retrospective application where an enforcement notice has already been issued, and making a related retrospective application can also restrict the ability to argue later, through a ground (a) enforcement appeal, that permission should be granted.

That is one reason retrospective consent should never be treated as a routine alternative to applying properly in advance. Besides the planning risk, it removes the opportunity to resolve problems before the money has already been spent building the scheme.

Enforcement: what a council can actually do

Planning enforcement is discretionary rather than automatic. A council deciding how to respond should consider the seriousness of the breach, its planning impact and whether formal action is expedient. Government planning enforcement guidance says formal enforcement will not always be appropriate for a trivial or technical breach that causes no material harm, or where the development is acceptable on its planning merits and an application is the appropriate way to regularise it.

Where a council does decide to act, its powers include a planning contravention notice, used to obtain information about a suspected breach; an enforcement notice, setting out what the council believes has gone wrong and the steps required to remedy it; a breach of condition notice; and, where rapid intervention is justified, stop notices and temporary stop notices.

Since 25 April 2024, councils in England have also been able to issue an enforcement warning notice where unauthorised development appears to have a reasonable prospect of being acceptable in planning terms. This formally invites a retrospective application by a specified date and itself counts as enforcement action for the purposes of the statutory time limits.

An enforcement notice has its own effective date and a separate period for carrying out the remedial steps it requires. An appeal against the notice must reach the Planning Inspectorate before the notice takes effect — not within the ordinary planning-appeal deadlines discussed elsewhere.

Ignoring an enforcement notice once it has taken effect and its compliance period has expired is a serious matter. Failure to comply, where there is no outstanding appeal, is a criminal offence and can result in an unlimited fine.

A temporary stop notice is different again: it can require an unauthorised activity to stop immediately without waiting for an enforcement notice to be issued first. In England, a temporary stop notice can now normally remain in force for up to 56 days, rather than the 28-day maximum that applied before 25 April 2024.

The current time limits — and why old advice about this may now be wrong

This is the part that most needs updating from whatever you might have read a few years ago.

Historically, English planning law drew a distinction between two enforcement time limits under section 171B of the Town and Country Planning Act 1990: four years for operational development — building, engineering or similar physical works — and for a change of use of a building to a single dwellinghouse, and ten years for most other breaches.

The Levelling-up and Regeneration Act 2023 changed that position in England. From 25 April 2024, the ordinary enforcement period for operational development and unauthorised changes of use to a single dwellinghouse increased from four years to ten years, bringing them into line with the existing ten-year period for most other breaches.

Crucially, the change was not applied retrospectively to the categories previously protected by the four-year period. The 2024 transitional regulations preserve the old rules where operational development was substantially completed before 25 April 2024 or an unauthorised change to use as a single dwellinghouse occurred before that date.

Which enforcement time limit applies?

These are the ordinary statutory limits, not guarantees that every old breach is immune. Previous enforcement action, concealment and other circumstances can alter the position.

For an English operational-development case that relies on the old four-year rule, the key question is therefore when the work was substantially completed. For an unauthorised change to a single dwellinghouse, the relevant question is when that breach occurred. If either date is disputed, evidence can become crucial.

Dated photographs, invoices, council-tax or utility material where relevant, contemporaneous correspondence and other reliable evidence can help establish the history. Simply saying “it’s been there for years” is unlikely to be enough where the date is challenged.

The jurisdiction point matters too. Wales retains the four-year and ten-year structure. Scotland also retains broadly equivalent four-year and ten-year periods under its own legislation.

Northern Ireland is different again: under the Planning Act (Northern Ireland) 2011, the ordinary enforcement time limit is five years, rather than the four-year/ten-year structure used in Wales and Scotland.

Don’t rely on a flat statement that “four years means it’s automatically lawful” anywhere in the UK without checking the type of breach, the relevant dates, whether enforcement action has already been taken and the jurisdiction involved.

Deliberate concealment changes the picture entirely

The expiry of the ordinary time limit does not necessarily protect development that has been deliberately concealed.

In England, a council can apply to a magistrates’ court for a planning enforcement order, allowing enforcement action to be taken notwithstanding the normal section 171B time limits where the apparent breach has been deliberately concealed. Government guidance also reflects court decisions in which deliberate concealment can affect when the normal enforcement clock begins to run.

This is aimed at genuine concealment rather than merely failing to volunteer the existence of unauthorised work. For a planning enforcement order, the council needs evidence of positive steps to conceal the development, and the court must be satisfied that concealment occurred and that making the order is just in all the circumstances.

Trying deliberately to hide or misrepresent unauthorised development is therefore a very different proposition from simply discovering years later that an old extension lacks the planning paperwork everyone assumed existed.

Lawful Development Certificates aren’t the same as planning permission

A Lawful Development Certificate can confirm that an existing use, operation or other activity is lawful for planning purposes.

That might be because planning permission was not required, because the development was carried out within an existing permission, or because the relevant period for enforcement has expired and the statutory test for lawfulness is met.

It is not retrospective planning permission. The council is not deciding whether it likes the development or whether it would approve the scheme if an application were made today. It is deciding a legal question: whether the development is lawful.

Where the relevant facts are historical, the quality of the evidence matters. The burden is on the applicant to provide enough information for the council to determine the question, and false or misleading information used to obtain a certificate can have serious consequences.

For a property transaction, a certificate can provide valuable formal evidence of the planning status of historic work, rather than leaving a buyer, lender or solicitor to rely simply on assertions about how long something has been there.

Buying, selling and unauthorised work

Unauthorised development surfacing during a sale is one of the more common situations in which the issue becomes commercially important, whether through a survey, a mortgage valuation or conveyancing enquiries.

It can prompt further questions from buyers, solicitors and lenders, delay exchange or become part of a price negotiation. The appropriate response — which might involve establishing that permission was never required, obtaining a Lawful Development Certificate, applying retrospectively or considering an indemnity product where appropriate — depends heavily on the facts.

Indemnity insurance is not a substitute for establishing the planning position, and its availability and usefulness depend on the particular transaction, lender and policy terms. Contact with the council can also affect whether some policies remain available, so this is an area where the order in which steps are taken can matter.

Our companion coverage in Conveyancing & Title deals with the transactional side in more depth; this article focuses on the planning position itself.

Planning lawfulness and Building Regulations compliance are two separate questions

A Lawful Development Certificate, or the expiry of a planning-enforcement time limit, says nothing about whether the work complied with Building Regulations.

Structural safety, fire safety, insulation, electrical work, drainage and other Building Regulations requirements operate under a separate legal regime with their own enforcement powers and time limits. In England, those enforcement powers were themselves substantially strengthened under the Building Safety Act 2022.

Work can therefore be lawful for planning purposes and still have Building Regulations problems, and vice versa. Treating one as proof of the other is a common and potentially costly mistake, and it’s covered properly in our dedicated Building Regulations article rather than here.

The reasonable takeaway

Unauthorised work isn’t automatically doomed — plenty of cases can be resolved because permission was never required, through a retrospective application, or by establishing that development has become lawful through the passage of the relevant enforcement period.

But equally, older work isn’t automatically safe just because “it’s been there for years”, particularly once the dates, type of breach, previous enforcement history and jurisdiction are checked against the current rules rather than against what used to be true.

Given how much financial and legal weight can rest on getting this right — particularly around a sale, a mortgage or a formal notice — this is one area of planning where it’s genuinely worth getting a professional assessment of the specific facts before deciding what, if anything, to do next.

This article provides general property information, not legal or planning advice for individual circumstances. Whether a specific piece of unauthorised work is enforceable, and what the best course of action is, depends on its exact nature, dates, enforcement history and location. If you’ve received a formal enforcement notice, or significant money or a property sale is at stake, take advice from a solicitor or planning consultant before acting.