How to apply for retrospective planning permission

What does section 73A actually allow?

Section 73A of the Town and Country Planning Act 1990 covers three situations: work carried out with no permission at all, work that outlived a temporary permission, and work that ignored a condition attached to a permission you did have. It is the route for anything that went past permitted development: a single-storey rear extension deeper than 3 metres on a terraced or semi-detached house, for example, or works in an area where an Article 4 direction removed the rights. A rear extension built with clear glazing where the permission required obscure glass, or a flat roof used as a terrace where a condition forbade it, is a breach just as much as a building nobody applied for.

A retrospective application is judged against the same Local Plan policies as any other. Government guidance is explicit that it must be considered in the normal way, on its planning merits, even where the council invited it. For the plain definition and how the term is used, see our glossary entry on retrospective planning. This guide is about doing it.

How do you apply, step by step?

1. Measure the building as it stands. The drawings must show what exists, not what the builder was told to build. Officers compare them with photographs and, often, a site visit. A small error in height at the boundary undermines everything else in the submission.
2. Draw existing and proposed. For retrospective work, "existing" is usually the house before the works and "proposed" is the house as it now stands. Include a location plan, block plan, floor plans, elevations and, where height at the boundary matters, a section.
3. Decide whether to offer changes. If part of the work is plainly unacceptable, such as a raised terrace overlooking a neighbour's garden, show it removed or screened on the drawings. Permission for a reduced scheme is better than refusal of the whole.
4. Tick the retrospective box. The application form asks whether the work has already started and, if so, when. Answer truthfully. The date matters for the time limits below.
5. Pay the fee and wait for validation. Councils aim to decide householder applications within eight weeks.

Sources: MHCLG, Planning fees: annual indexation from 1 April 2026; MHCLG, Planning applications in England: January to March 2026. Both retrieved 12 September 2026.

The 90% grant rate is a national figure for all householder applications. MHCLG does not publish a separate rate for retrospective ones, so treat it as the ceiling, not your odds.

How long does the council have to take action?

The Levelling-up and Regeneration Act 2023 changed section 171B of the 1990 Act. Before the change, building operations became immune from enforcement four years after substantial completion. Now the period is ten years for everything in England. The transitional rule in regulation 5 of SI 2024/452 keeps the four-year limit for operations substantially completed, and changes of use to a single house that happened, before 25 April 2024.

Sources: Town and Country Planning Act 1990, s.171B; SI 2024/452, regulation 5; GOV.UK, Enforcement and post-permission matters. Retrieved 12 September 2026.

If your work is already past its limit, a retrospective application is the wrong tool. A Lawful Development Certificate for an existing development asks the council to confirm the work is immune. It turns on dated evidence: invoices, building control completion certificates, dated photographs, council tax records.

What are the risks of applying?

• The one-chance rule. Government guidance says a person who has carried out unauthorised development has only one opportunity to get permission afterwards: either a section 73A application or a ground (a) appeal against an enforcement notice, not both.
• Lost ground (a). Under section 174(2A), if the council issues an enforcement notice after your related application, you cannot argue on appeal that permission ought to be granted, unless the notice comes more than two years after the application stopped being under consideration.
• The council can decline to decide. Section 70C lets it refuse to determine a retrospective application if an enforcement notice covering the same work was issued first.
• Community Infrastructure Levy. In a CIL charging area, retrospective permission is not eligible for reliefs or exemptions other than the minor development exemption.
• Selling the house. A buyer's solicitor will ask for the permission. A refusal on the public register is harder to explain than an application never made, so apply with a scheme that can win.

What happens if it is refused?

You can appeal. For a householder refusal the Planning Inspectorate must receive the appeal within 12 weeks of the decision date, cut to 28 days where an enforcement notice on the same development was served within the two years before your application. Appeals on applications made on or after 1 April 2026 follow the written "part 1" procedure: no new evidence, so the drawings you submitted are the drawings the inspector judges. Our planning appeal service sets out the fees and published timings.

The council may instead, or as well, serve an enforcement notice. That starts its own clock, explained in our guide to receiving a planning enforcement notice.

When should you apply rather than wait?

Apply once a neighbour has complained, the council has written to you, or you are about to sell. A planning contravention notice has to be answered within 21 days, and failing to reply is itself an offence under section 171D. An enforcement warning notice under section 172ZA, introduced on 25 April 2024, is the council formally inviting an application by a set date. There is no appeal against it, and it counts as enforcement action for the time limits.

Waiting in the hope of reaching immunity means ten years for anything finished since 25 April 2024, and every one of those years is a sale or remortgage where the question can come up.