Retrospective Planning Permission in London: How It Works (2026)
How retrospective planning permission works in London — the s73A application process, the new 10-year enforcement rule, certificates of lawfulness, and the drawings you need.
Retrospective planning permission is what you apply for when work that needed planning consent has already been carried out without it — an outbuilding that overstepped permitted development, a rear extension built deeper than allowed, a loft dormer facing the highway, or a change of use the council never approved. It exists because building without permission is not automatically a criminal act in England, but it does leave the development unauthorised and exposed to enforcement until the position is regularised. This guide explains how the process actually works in London, in plain terms.
The important thing to grasp up front is that a retrospective application is not a lighter-touch route or a formality. The council assesses it against precisely the same local plan and national policy it would have used before a brick was laid, and it can refuse. What changed dramatically in 2024 is the enforcement clock: the long-standing four-year immunity for building work was abolished and replaced by a single ten-year period for almost every breach. That single change makes understanding your real options — regularise, certify, or wait — more valuable than ever for London homeowners.
What is retrospective planning permission?
Retrospective planning permission is a full planning application for development that has already been built or a use that has already begun. The legal basis is section 73A of the Town and Country Planning Act 1990, which lets a local planning authority grant permission for operations already carried out. In practice you complete the same householder or full planning application you would have submitted beforehand, pay the same statutory fee, and the council determines it against the same policies within the same target period — usually eight weeks for a householder application.
There is one crucial difference in mindset. Because the work is on the ground, the officer is judging real harm rather than a proposal on paper, and a neighbour who has lived beside an overbearing extension for a year may object more forcefully than they would have to a drawing. Retrospective permission does not wipe the slate clean either — it simply grants consent going forward. If it is refused, the development remains unauthorised and the council can move to enforcement.
How does the retrospective application process work?
The process mirrors a standard application almost exactly. You submit existing and proposed drawings, the correct forms, the fee and any required statements through the Planning Portal; the council validates it, consults neighbours and statutory consultees, and an officer assesses it against the development plan before issuing a decision. The only structural difference is that the "proposed" scheme already exists, so your drawings must show the building as actually constructed, not an idealised version.
Where the built work would fail policy, applicants sometimes submit a retrospective application for a modified scheme — proposing to reduce a bulk, add obscure glazing or lower a ridge — so that the permission granted is achievable and the remaining work brings the building into line. Getting the drawings right is the pivot of the whole exercise: an application that does not honestly match what a planning enforcement officer will measure on site invites refusal, and accurate as-built drawings are exactly what a practice like DrawingsDirect prepares so the submission reflects reality and stands the best chance of approval.
The s73A retrospective application route
A section 73A application is made when you actively want permission for the unauthorised work — typically because it is not yet immune from enforcement, or because you need a clean planning history to sell or remortgage. You lodge it like any householder or full application, and the council can grant it unconditionally, grant it with conditions, or refuse. If granted, the development is lawful from that point. If refused, you have the usual right of appeal to the Planning Inspectorate, and the council may run enforcement in parallel. The application fee for a retrospective householder submission is the same nationally set charge as a normal one, and there is no penalty loading beyond the ordinary fee.
The certificate of lawfulness (CLEUD) route
If the work is old enough to be immune from enforcement, you do not seek permission at all — you apply for a Certificate of Lawfulness of Existing Use or Development under section 191. A CLEUD does not judge whether the development is acceptable; it certifies that it is now lawful because the time limit for enforcement has passed. The burden of proof sits entirely on you, on the balance of probabilities, so you need dated evidence — invoices, photographs, utility records, statutory declarations from neighbours — proving continuous existence for the full immunity period. Get it and the development is unassailable; the certificate is the document a conveyancing solicitor will ask for.
What are the 4-year and 10-year enforcement rules?
Enforcement immunity is the heart of the whole subject. Historically, operational development (building work) and the change of use of a building to a single dwelling became immune from enforcement after four years, while other changes of use and breaches of condition took ten years. That four-year shortcut is what fuelled the old "just build it and wait" gamble. The Levelling-up and Regeneration Act 2023 swept it away.
From 25 April 2024, the immunity period for breaches of planning control in England became a single ten years for almost every type of breach. Building work completed on or after that date must now stand unchallenged for a full decade — not four years — before it can become lawful through the passage of time. Work substantially completed before 25 April 2024 generally keeps the old four-year clock under transitional provisions, which is why the exact completion date matters so much and why dated evidence is worth gathering early.
- Before 25 April 2024: 4 years for building operations and change to a single dwelling; 10 years for other uses and condition breaches.
- From 25 April 2024: a single 10-year immunity period for substantially all breaches of planning control.
- Transitional rule: work substantially complete before the cut-off date can still rely on the old 4-year period.
- Immunity from enforcement is not the same as planning permission — it only removes the council's power to act after time has run.
- The clock runs from substantial completion of the building work, or from the date a breach of condition or unauthorised use began.
Why is "easier to ask forgiveness" a myth?
The folk wisdom that it is easier to build first and apologise later is genuinely dangerous, and the 2024 reforms made it worse. A retrospective application can be refused just like any other, and refusal leaves you exposed to a planning enforcement notice requiring the unauthorised work to be altered or removed entirely — at your expense. You can appeal a notice, but if the appeal fails you must comply, and failing to comply with an enforcement notice is a criminal offence carrying an unlimited fine.
The commercial risk is just as real. An unauthorised extension or loft with no permission and no certificate is a red flag on any conveyancing search, and buyers' solicitors routinely require the position to be regularised before completion — which can collapse a sale or force a rushed, weak application. With the immunity period now ten years rather than four, the "wait it out" strategy ties up the property far longer than most homeowners expect. Applying properly, with honest as-built drawings, is almost always cheaper and faster than living with the uncertainty.
Do London boroughs enforce retrospective breaches?
Yes, and enforcement practice varies noticeably across the 33 London boroughs. Enforcement is discretionary — a council acts where it judges it "expedient" in the public interest — but London authorities receive high volumes of complaints, particularly in dense terraced streets where a neighbour quickly notices an oversized rear extension or a new roof. Boroughs with strong conservation-area coverage and active Article 4 directions tend to investigate more readily, because permitted development rights there are already restricted.
A council's typical first step is a planning contravention notice or an informal request for information, often followed by an invitation to submit a retrospective application to regularise the position. If that is ignored, or the application is refused, the authority can serve an enforcement notice, a breach of condition notice, or in urgent cases a stop notice. Listed-building breaches are treated far more seriously and can be prosecuted directly. The safest position anywhere in London is a valid permission or a certificate of lawfulness on file.
What drawings do you need for a retrospective application?
A retrospective or lawfulness application needs the same drawing package as any planning submission, with one defining feature: the "proposed" drawings must depict the building exactly as it was actually built. You need existing (as-built) plans, elevations and often sections drawn to a recognised metric scale, a location plan at 1:1250 and a block plan at 1:500 with the site edged red, all produced from an accurate measured survey of the completed work. Where you are regularising a modified scheme, a genuine proposed set shows the changes that will bring the building into line.
For a CLEUD, the drawings are supported by the dated evidence that proves elapsed time, so the survey and the paperwork work together to demonstrate exactly what exists and how long it has existed. Precision matters more than in a normal application because an enforcement officer can and will measure the building against your submitted drawings; any discrepancy undermines the whole case. Commissioning an accurate as-built survey and a coordinated drawing set is the single most useful step, and it is the stage where getting it right first time avoids a refusal on grounds of an inaccurate application.
| Route | When it applies | What the council decides | Key evidence |
|---|---|---|---|
| Retrospective permission (s73A) | Work is not yet immune from enforcement | Whether the built development is acceptable on planning policy | As-built + proposed drawings, statements |
| Certificate of lawfulness (CLEUD, s191) | Work has passed the immunity period | Only whether it is now lawful by elapsed time | Dated proof of continuous existence + drawings |
| Do nothing | Neither immune nor regularised | Nothing — but retains the power to enforce | None; leaves the property exposed |
Related services: Planning Permission, Planning Drawings, Lawful Development Certificate Drawings.
Frequently asked questions
Is it illegal to build without planning permission in England?+
How long does unauthorised work take to become lawful now?+
Can a council refuse retrospective planning permission?+
What is the difference between retrospective permission and a certificate of lawfulness?+
Do I need new drawings for a retrospective application?+
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