The 4-Year Rule Has Changed: Planning Enforcement Time Limits in England (the 10-Year Rule Explained)

01

The short answer: which time limit applies in England?

Sources: TCPA 1990 s171B(1)–(3) and (2A) as amended by Levelling-up and Regeneration Act 2023 s115; SI 2024/452 reg 5; PPG Enforcement 17b-004 (revised 25 April 2024); Planning (Listed Buildings and Conservation Areas) Act 1990 s9 and s38.

"Immune" means the council can no longer take enforcement action. It does not mean the work was ever granted planning permission, and it does not cover building regulations, a listing or a covenant. To prove immunity, see the lawful development certificate section below.

02

What changed on 25 April 2024

Section 115 of the Levelling-up and Regeneration Act 2023 rewrote the first two subsections of s171B. For England it replaced "four years" with "ten years" for operational development and for a change of use of a building to a single dwellinghouse. For Wales it kept four years. It came into force on 25 April 2024 under regulation 3(b) of SI 2024/452.

The change was not retrospective. Regulation 5 reads:

"The amendments made to the 1990 Act by section 115 of the 2023 Act (time limits for enforcement) do not apply where— (a) in respect of a breach of planning control referred to in section 171B(1) of the 1990 Act (time limits), the operations were substantially completed, or (b) in respect of a breach of planning control referred to in section 171B(2) of the 1990 Act (time limits), the breach occurred, before the day on which that section comes into force."

Read it closely, because it is narrower than the way it is usually repeated:

• For building work the test is when the operations were substantially completed. If they were substantially completed before 25 April 2024, the old 4-year limit applies. If building began in 2022 and finished in June 2024, the work was not substantially completed before the cut-off, so the 10-year limit applies.
• For a change of use to a single dwellinghouse the test is when the breach occurred.
• It is not a rule about "breaches that happened before 25 April 2024" in general. The Planning Practice Guidance states the same split: 10 years where substantial completion or the change of use was on or after 25 April 2024, and 4 years where it was before (PPG Enforcement 17b-004).

You may read that "the 4-year rule applies if the building work began before April 2024". That is not what regulation 5 says.

03

Which clock applies to you? A decision flow

1. Is the problem building work, or a change of use? Building, engineering and other operations follow s171B(1). A change of use follows s171B(2) if the building became a single dwellinghouse, or s171B(3) for any other change of use.
2. If building work: when was it substantially completed? Before 25 April 2024 means 4 years from that date. On or after it means 10 years. If you cannot fix a date, read the section on "substantially completed" below.
3. If a change of use to a single home: when did the change of use occur? Before 25 April 2024 means 4 years. On or after it means 10 years.
4. Is it a breach of a condition, or any other breach? 10 years from the breach (s171B(3)).
5. Has the council taken enforcement action in the last 4 years? If it has, "further" action may still be possible (see "What counts as enforcement action, and the rolling 4-year window").
6. Was anything concealed, or is a listed building or conservation-area demolition involved? Different rules apply (see "Exceptions").

If a building was built without permission and is also being used as a separate home, there are two breaches, each with its own clock: the operations under s171B(1) and the change of use under s171B(2).

04

Worked examples with dates

These are arithmetic from the statute, not a prediction about what a council will do. The statute counts the period as "beginning with" the completion date, so the last day to act falls shortly before the anniversary.

Basis: s171B and SI 2024/452 reg 5.

The garden-room example matters. If the same garden room was built in 2022 without permission and used as a home from 2025, the building work and the new use are separate breaches under s171B(1) and (2), so one may be time-barred while the other is not. Take advice before assuming a building that has become immune can lawfully be lived in.

05

What "substantially completed" means

Section 171B does not define it. The Planning Practice Guidance simply says time runs "within 10 years of substantial completion" for operational development (PPG Enforcement 17b-004). The leading authority is the House of Lords in Sage v Secretary of State for the Environment, Transport and the Regions [2003] UKHL 22 (also on BAILII). Mr Sage began building a house without permission and stopped short of completing it. The council served an enforcement notice in March 1999. The Lords held that the whole operation of building the house is looked at, and that regard should be had to the totality of the operations the person originally contemplated and intended to carry out. Where no application was made, evidence of the intention can come from the building's physical features and design.

In practice this means:

• A building that is watertight on the outside but still needs the internal fit-out that was always intended may not be "substantially completed", so the clock may not have started.
• Where a building is not built fully in accordance with its permission, the House of Lords treated the whole operation as unlawful rather than a series of separate small ones.
• Proving a completion date is a question of evidence, such as dated photographs, invoices, utility connections and aerial images, and you carry the burden on a certificate application (see below).

06

What counts as enforcement action, and the rolling 4-year window

Nothing in s171B suspends the time limit. What the limit does is stop the council "taking enforcement action" after the period ends, so action taken in time is valid. What counts as taking enforcement action is defined in s171A(2):

• the issue of an enforcement warning notice in England (new from 25 April 2024; s172ZA);
• the issue of an enforcement notice;
• the service of a breach of condition notice.

A planning contravention notice and an informal letter are not on that list. An enforcement warning notice is: it tells the owner that further enforcement action may follow unless an application is made within a stated period, and it counts as enforcement action (s172ZA; PPG 17b-013c).

Taking action in time matters because of a further rule. Section 171B(4)(b) allows the council to take "further enforcement action" on the same breach if, "during the period of four years ending with that action being taken", it has "taken or purported to take enforcement action in respect of that breach". That is a rolling four-year window from the last action, not an indefinite suspension. The PPG calls it the "second bite" and notes that it covers an earlier notice that turned out to be defective, and a warning notice followed by further action (PPG 17b-004). So "the council did nothing for years" is not safe if a warning notice or notice was issued in time.

07

Exceptions: concealment, listed buildings and conservation areas

Deliberate concealment. The council can apply to a magistrates' court for a planning enforcement order (s171BA). If the court makes one, the council can take enforcement action "at any time in the enforcement year", whether or not the s171B period has expired. The application must be made within 6 months of the day evidence sufficient to justify it came to the council's knowledge (s171BB). The court must be satisfied on the balance of probabilities that the breach has "(to any extent) been deliberately concealed" and that an order is just (s171BC). The PPG says the order is aimed at positive steps to conceal, "rather than merely refraining from informing" the council (PPG 17b-026).

Separately, the Supreme Court held in Secretary of State for Communities and Local Government v Welwyn Hatfield Borough Council [2011] UKSC 15 that an owner who built a house that looked like a permitted barn, using deceptive planning applications to avoid enforcement for the then 4-year period, could not rely on the time limit. Lord Mance said that "positive and deliberately misleading false statements by an owner successfully preventing discovery take the case outside" the rationale for the limit (para 54). Councils can use the PEO route or serve an enforcement notice "out of time" in such cases (PPG 17b-004). While the PEO route is still open, a certificate application cannot treat the time as expired (s191(3A)).

Listed buildings. The 4- and 10-year limits are in the planning Act and do not govern listed building enforcement. Executing works to a listed building without consent is a criminal offence under LBCA 1990 s9, and the listed building enforcement power in s38 has no equivalent time limit. Do not assume anything done to a listed building becomes immune. See our guide to listed building consent.

Conservation-area demolition. There is "no restriction on when enforcement action may be taken" for relevant demolition (s171B(2A); definition in s196D).

Breach of condition. A breach of a planning condition is an "other breach", so 10 years (s171B(3)).

08

Proving immunity: the lawful development certificate

If the time has run, a lawful development certificate (LDC) is how you prove it. Under s191, a use or operations are lawful if no enforcement action may then be taken because "the time for enforcement action has expired", and a certificate, once granted, conclusively presumes lawfulness (s191(6)).

• Evidence. The applicant provides it. If the council has no contrary evidence, the application can succeed if the applicant's own evidence is "sufficiently precise and unambiguous" on the balance of probability (PPG Lawful development certificates 17c-006).
• Fee (England, from 1 April 2026). For existing use or operations the fee is the same as the full planning fee: £548 for a householder extension and £272 for outbuildings and similar works (MHCLG fee schedule). Fees rise each 1 April, so check the current schedule.
• What it does not do. It does not grant permission and does not deal with building regulations.

Our guide to the lawful development certificate covers the application step by step. If the building is not yet immune and you want to regularise it, see retrospective planning permission.

09

Building regulations run on a different clock

Planning immunity does not protect against building regulations. In England the council can serve a notice requiring work that breaches the regulations to be pulled down or altered, and since 1 October 2023 that notice can be given up to 10 years from completion, where the limit used to be 12 months (Building Act 1984 s36(4), as amended by Building Safety Act 2022 s39(3)). The only transitional saving is for notices given before that date (SI 2023/993 reg 7(2)). There is also an injunction route in s36(6) with no statutory time limit. An owner can apply for a regularisation certificate for unauthorised work carried out on or after 11 November 1985 (Building Regulations 2010 reg 18).

10

Wales, Scotland and Northern Ireland

Everything above is England. Do not apply these limits elsewhere.

Wales is moving to a consolidated Planning (Wales) Act 2026, which received Royal Assent on 27 April 2026. The Welsh Government says the existing framework applies until commencement, which it expects around October 2027 (Welsh Government: consolidation of planning law). Appeals sit with Planning and Environment Decisions Wales in Wales, the Planning and Environmental Appeals Division in Scotland and the Planning Appeals Commission in Northern Ireland. The Building Act s36 10-year limit applies in Wales from 1 July 2026 (Building Act 1984 s36).

11

Why so many forum answers are still wrong

Search results and old threads still repeat "4 years" because that was the rule for decades and the change was not retrospective. The common mistakes are:

• "4 years still applies." Only for work substantially completed (or a home created) before 25 April 2024.
• "The clock starts when work began." For building work it starts at substantial completion (s171B(1)).
• "If the council hasn't acted by year X, it can't." An enforcement warning notice or earlier action can keep the position open (s171A(2), s171B(4)(b)).
• "Listed works become immune." They do not.
• "A converted outbuilding is 4 years." Since 25 April 2024 a new conversion to a single home is 10 years.

13

Where to go next

• Building something now, or built something that needs regularising: retrospective planning permission.
• Proving a building is lawful: lawful development certificate cost and how to apply.
• Received a letter or notice: planning enforcement, from the first letter to an enforcement notice.
• Reporting a neighbour: what to do if a neighbour builds without permission.
• Garden cabins: log cabin built without planning permission.

Search planning applications and history near you

This guide is general information, as at October 2026, and not legal advice. Whether a specific building is immune depends on evidence of its completion date and use.