Retrospective applications under section 73A

A retrospective planning application is made under section 73A of the Town and Country Planning Act 1990, and it does exactly what an ordinary application does except that the building is already there. It does not make unauthorised work lawful by being submitted, it does not pause enforcement, and in some circumstances the council can refuse to determine it at all. For a householder who has built an extension bigger than the plans allowed, it is still usually the right move, provided you understand what it buys and what it costs.

What section 73A allows

Section 73A lets an authority grant planning permission for development already carried out, for development carried out without complying with a condition, and for the retention of buildings or works without complying with a condition.

Permission granted this way can take effect from the date the development was carried out. That retrospective effect is what regularises the position, and it is why the section exists.

The assessment is the same as for any application. Officers apply the development plan and any other material considerations, and the fact that the work is built is not itself a reason to grant. It is also not a reason to refuse. An inspector will say, and councils sometimes need reminding, that the merits are judged as though the application had been made in advance.

Applying for development already carried out

The paperwork is ordinary, with one difference: the drawings must show what exists, measured, rather than what was intended.

Have the extension or the works surveyed properly. A retrospective application drawn from the original approved drawings with a note saying "as built" invites a refusal, because the officer cannot tell what they are being asked to permit. Dimensioned plans, elevations and a section, plus a site plan with the correct footprint, are the minimum.

Two supporting documents usually help:

• a short planning statement explaining what was built, how it differs from any previous permission, and why it complies with policy
• photographs of the completed work from the street and from the affected neighbouring boundary

Describe the development accurately on the form. "Retention of single storey rear extension as built" is better than a description copied from the earlier permission, and an inaccurate description can undermine any permission that follows.

Whether a retrospective application affects enforcement

Submitting an application does not stop the council serving an enforcement notice, and it does not create any immunity while it is under consideration. In practice many authorities hold off, because an enforcement notice would be premature while a decision is pending, but nothing obliges them to.

Section 70C of the 1990 Act runs the other way and matters more. Where an enforcement notice has already been issued, the authority may decline to determine a retrospective application for any part of the matter stated in that notice. The order in which things happen therefore decides what routes remain open, which is a reason to apply before a notice lands rather than after.

The Levelling-up and Regeneration Act 2023 made further changes to enforcement, including the time limits after which a breach becomes immune, which for England moved to ten years. Commencement dates and transitional arrangements apply, so check the position for the date the work was carried out rather than assuming the current rule always applied.

Fees and the loss of any free resubmission

A retrospective application attracts the same fee as the equivalent application made in advance, set by the national fee regulations and indexed annually from 1 April. Check the current schedule.

The concession most householders lose is the free resubmission. The right to submit a further application without a fee, within a year of a withdrawal or refusal, does not apply where the earlier application was retrospective. So a refused retrospective application followed by a revised scheme means a second full fee.

Budget for a possible second application from the start. The most common outcome on an overbuilt extension is not refusal of everything, but a negotiated reduction, and that reduction generally needs its own application.

Risks of applying rather than waiting

The argument for doing nothing is that enforcement is discretionary, councils are stretched, and immunity arrives with time. The argument against is that the risk sits on the property until then.

An unauthorised extension shows up on a sale. Conveyancing enquiries ask about building work in the last ten years, indemnity insurance is not always available, and a buyer's solicitor who spots an extension with no permission and no certificate will hold up the transaction. The cost of that delay usually exceeds the cost of the application.

Applying does draw attention. A case officer visits, neighbours are consulted, and a scheme that nobody had complained about becomes visible. That is a real risk and it should be weighed honestly, particularly where the work affects a neighbour who has not yet noticed.

Where the application is refused, the council is more likely to enforce, because the merits have been tested and found wanting. An appeal under section 78 is available, generally within six months for a full application and twelve weeks for a householder application. Where the council neither grants nor refuses, the appeal against non-determination remains open in the usual way.

An illustrative example

A rear extension is built 4.2 metres deep where the approved drawings showed 3 metres, and the roof is a flat roof rather than the approved pitched one. The owner applies retrospectively. The officer raises no objection to the depth but considers the flat roof harmful to the pair of semis. A revised application, at a second fee, proposes a shallow pitched roof and is approved. This example is illustrative.

Evidence to submit with the application

Beyond the measured drawings, put in whatever answers the objection the officer is most likely to receive.

1. A section through the relationship with the neighbouring property, where the concern will be light or enclosure.
2. Photographs from inside the affected neighbouring room, if the neighbour is content.
3. Materials evidence, with a photograph of the brick and a note of the match to the host dwelling.
4. Drainage details where the footprint has increased and surface water is a question.
5. The date the work was completed, stated plainly, because it affects the enforcement position.

Understating the extent of what was built is the mistake that turns a survivable application into a refused one. Officers measure.

Where a lawful development certificate is better

If the work is already immune from enforcement, a retrospective application is the wrong tool. A certificate of lawfulness of existing use or development under section 191 of the 1990 Act asks whether the development is lawful, not whether it is acceptable, so the merits do not arise.

That route needs evidence of the date of substantial completion and of continuous existence since: dated photographs, invoices, delivery notes, council tax or utility records, and statutory declarations from people who can speak to the facts. The burden is on the applicant and the standard is the balance of probabilities.

It is also the right tool where the work was permitted development all along and the only problem is proving it. Many householder extensions that owners assume are unauthorised were lawful from the day they were finished. Check the permitted development limits before applying for anything.

Browse all 66 PlanScope report types to see what a retrospective application on your property is likely to need.

This is general guidance, not legal advice; check the position with your local planning authority or a qualified professional before relying on it. A lawful development certificate is the only formal way to confirm that works are lawful. PlanScope provides AI-assisted draft reports for planning applications. Reports should be reviewed before submission. We do not guarantee planning approval.