Enforcement warning notices under the 2023 Act

An enforcement warning notice planning letter is not an enforcement notice. It is a formal invitation to apply for permission for something you have already done, served when the council thinks there is a realistic prospect that permission would be granted. Ignore it and the council can move to formal enforcement. Respond to it and you get the merits of your development considered properly.

The power sits in section 173ZA of the Town and Country Planning Act 1990, inserted by the Levelling-up and Regeneration Act 2023. The 2023 Act's enforcement provisions have been brought into force in stages by regulations, so if this matters to a live case, check the current position on legislation.gov.uk rather than assuming. As at September 2026 the power exists and authorities in England are using it.

What an enforcement warning notice is

The conditions for serving one are specific. It appears to the local planning authority that there has been a breach of planning control, and there is a realistic prospect that planning permission would be granted if an application were made for the development in question.

The notice must set out the matters that appear to constitute the breach and state that, unless an application is made within a specified period, further enforcement action may be taken.

That is the whole mechanism. No fine, no requirement to demolish anything, no immediate consequence beyond a deadline and a stated intention.

Two things it is not. It is not a determination that you are in breach; that remains an allegation until it is established. And it is not a promise that permission will be granted, only the authority's view that the outcome is realistically available.

Where it sits between informal contact and formal action

Enforcement has always had an informal stage. An officer visits, writes a letter, asks what is going on, suggests an application. That stage works, most of the time, and nothing in the 2023 Act removed it.

The problem it was meant to solve is the case that stalls. A breach exists, the development would probably be acceptable, and the owner does nothing because an informal letter carries no deadline. The authority is then left choosing between enforcement action against development it would have permitted, or doing nothing.

A warning notice gives the authority a formal, recorded step with a date on it, without committing to the consequences of an enforcement notice. It is proportionate, and it shifts the initiative to the recipient.

For a neighbour who reported the breach, this is the stage where it can look as though nothing is happening. It is not nothing. A warning notice is a documented step in a process, and if the invitation is not taken up the authority's position on expediency becomes considerably easier to defend.

The invitation to apply retrospectively

A retrospective application is an ordinary planning application for development already carried out. Same forms, same fee categories, same determination periods, same publicity. The fee is not increased because the work has been done, and fees are indexed annually, as covered in our note on annual fee indexation.

What the application needs to do is address the reasons the development would otherwise be unacceptable. So the supporting material matters more than usual. A Planning Statement dealing directly with the harm the officer identified, plus accurate drawings of what has actually been built, is the core of it. Measure what is there rather than submitting the drawings you built from, because the discrepancy between the two is often why the breach exists.

There is a strategic reason to take the invitation seriously, and it is the most useful point on this page. Section 70C of the 1990 Act allows an authority to decline to determine a retrospective application where an enforcement notice has already been issued for the same matter. Apply while you have a warning notice and that door is open. Wait until an enforcement notice arrives and it may close.

What happens if the invitation is ignored

The authority can then do what it said it might. In practice that means one of:

• An enforcement notice under section 172, specifying the breach and the steps required to remedy it, with a compliance period.
• A breach of condition notice, where the issue is non compliance with a condition on an existing permission.
• A stop notice or temporary stop notice, where the activity needs to cease quickly.
• Prosecution for non compliance with a notice once the compliance period has passed.

The warning notice itself is not a precondition for any of these, and an authority can go straight to an enforcement notice if it chooses. What the warning does is make the later decision easier to justify, because the authority has offered the lawful route and it was declined.

Time limits matter here, and they changed. The 2023 Act extended the immunity period for most breaches in England to ten years, replacing the previous four year rule for building works and for change of use to a single dwellinghouse. Breaches that had already become immune before the change keep that immunity, so the position depends on when the breach occurred. This is exactly the sort of point on which to take advice rather than to reason from a summary.

Appeal rights and their limits

There is no right of appeal against an enforcement warning notice. That surprises people, and it is deliberate: the notice imposes no obligation, so there is nothing to appeal against.

What you can do:

1. Make the application it invites, and appeal to the Planning Inspectorate if it is refused.
2. Apply instead for a lawful development certificate under section 191, if your position is that the development is already lawful because it is permitted development or immune by lapse of time.
3. Challenge the notice by judicial review, which is available in principle where an authority has acted unlawfully but is rarely proportionate at this stage.
4. Do nothing and appeal any subsequent enforcement notice on the grounds in section 174, which include that planning permission ought to be granted.

Option two is worth thinking about carefully. If you are confident there is no breach, a certificate application settles the question and produces a document you can rely on later, when you sell. If you are not sure, applying for a certificate and failing tells the authority the development is unlawful.

How the power is being used

Honest answer: unevenly, and the picture is still forming. Enforcement teams are resourced very differently between authorities, and a tool that creates a recorded step with a deadline appeals more to a team with capacity to follow it up.

What can be said without speculating about particular councils is that the notice is most useful in a specific kind of case. Householder development that overshot a permitted development limit. A change of use that would be acceptable subject to conditions on hours or noise. A building put up without permission that sits comfortably within local policy. Cases like the ones in our note on permitted development limits for solar panels on commercial roofs, where the principle is fine and the detail went wrong.

It is much less useful where the development is plainly unacceptable, because the statutory test is not met. If you receive one, that in itself tells you the officer thinks permission is realistically available.

What to do on receiving one

In order:

1. Read the description of the breach and check it against what is actually on site. Officers sometimes describe a breach imprecisely, and the description shapes everything that follows.
2. Note the deadline and put it somewhere that will remind you three weeks before.
3. Work out whether the matter might already be immune, given when it happened and the time limits applying to it.
4. Decide between a retrospective application and a certificate application. They are alternatives, and choosing wrongly is expensive.
5. Get accurate measured drawings of what exists.
6. Reply in writing, saying what you intend to do and by when, even if the answer is that you need more time.

Do not demolish anything in a panic. And do not assume that an informal conversation with the officer replaces a response to a formal notice, because the notice records a date and the conversation does not.

If you are following the wider set of changes the 2023 Act made, our planning law updates timeline is where new items are collected as they are confirmed.

This is general guidance, not legal advice. Enforcement time limits and the dates provisions came into force turn on precise facts and on regulations that have been brought into force in stages, so check the position with your local planning authority or a qualified professional before relying on it.

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