Under-enforcement and the rights it creates

Under-enforcement happens when an enforcement notice requires less than it could have required, and the consequence is written into the statute. Section 173(11) of the Town and Country Planning Act 1990 provides that where a notice could have required buildings or works to be removed, or an activity to cease, but does not do so, then on compliance with all the requirements of the notice planning permission is treated as having been granted under section 73A for what was left alone.

So a notice can hand an owner a lawful position that the authority never meant to give them. It is one of the few places in the enforcement regime where reading the document carefully is worth real money.

What under-enforcement means in practice

Compare two parts of any enforcement notice: the matters alleged to constitute the breach, and the steps required or activities required to cease. Where the second is narrower than the first, the gap is potential under-enforcement.

The usual reasons for the gap are sensible ones. An authority may consider that requiring full removal is disproportionate, that part of the development is acceptable, or that a lesser requirement will remedy the injury to amenity. Sometimes the gap is simply a drafting slip. Section 173(11) does not distinguish between the two.

The other common source is variation on appeal. An inspector who narrows the requirements under ground (f), because the steps required exceed what is necessary, can produce under-enforcement in a notice that did not originally contain any.

The statutory consequence of complying

The permission arises on compliance, not on receipt of the notice. Every requirement has to be met, and met within the compliance period, before section 173(11) bites.

What is granted is permission under section 73A for the development that the notice did not require to be undone. That is a permission for what physically exists or what continues to happen, and it comes without the conditions an authority would have imposed had it granted permission on an application. There is no design review, no section 106 and no opportunity to attach hours of operation.

That last point is why authorities take the drafting seriously. A notice that requires a takeaway to stop trading after 11pm, and nothing else, gives the operator a lawful hot food use until 11pm once they comply.

Why it can grant a use the notice never intended

The mechanism is mechanical rather than purposive. The question is what the notice could have required and did not, judged against the matters alleged, and the authority's intention is not the test.

Two patterns come up repeatedly. A building case, where the notice requires part of a structure to be removed and is silent on the rest, so the rest becomes lawful. And a use case, where the notice requires a use to cease in part, whether by area, by hours or by intensity, so the remainder becomes lawful.

A third pattern, less obvious, involves notices that require works to be altered rather than removed. Requiring a window to be obscure glazed, or a roof to be lowered, accepts the rest of the structure and confers permission for it on compliance.

How authorities draft to avoid it

The standard defensive technique is to require complete removal or complete cessation and then invite an application for whatever should remain, so that the authority keeps control over conditions. It is blunt and it works.

The alternative, used where full removal really would be disproportionate, is to draft the requirements to track the matters alleged exactly, so that no gap opens. Authorities that do this well describe the breach narrowly in the first place rather than describing it broadly and then requiring less.

Where an authority has under-enforced deliberately, it will sometimes say so in the reasons. That does not change the legal effect, and an owner who complies still gets the permission.

An illustrative example shows the effect. A rear outbuilding is converted to a self contained annexe and occupied independently. The notice alleges a material change of use to a separate dwelling and the unauthorised conversion works, and requires only that the independent residential occupation cease and the kitchen be removed. It says nothing about the shower room, the internal partitions or the separate access. On full compliance, those works become lawful under section 173(11), and the building is now a fitted outbuilding with a bathroom rather than a shell. This example is illustrative.

Identifying it when reading a notice

Read the notice in this order. First the matters alleged, and write them out as a list. Then the requirements, as a second list. Then map one onto the other and mark anything in the first list that has no corresponding requirement.

Check the plan as well as the text. A notice whose requirements apply to an area shown edged red on a plan, where the alleged breach covers a larger area, is under-enforcing on the difference even if the words do not say so.

Then check the compliance period and work out what full compliance would actually involve, physically and commercially. The permission only arrives if every requirement is met.

One further check is worth making before relying on any of this. Under-enforcement gives permission for what the notice left alone, and nothing more. It does not cure a separate breach that the notice never alleged, it does not deal with listed building consent or building regulations, and it does not assist where the works also need consent under another regime. Read the gap narrowly rather than generously.

Using it as an argument on appeal

An owner who spots under-enforcement in their favour often has a choice between appealing and complying. Complying is sometimes the better commercial answer, because it produces a lawful position without the cost and delay of an appeal and without the risk that the authority serves a better notice.

Where an appeal is going ahead anyway, ground (f) is the route to creating under-enforcement, by arguing that the steps required exceed what is necessary to remedy the breach or the injury to amenity. Inspectors vary requirements on that ground frequently, and the resulting narrower notice can carry a section 173(11) consequence the authority did not anticipate.

Be careful about advertising the point. An authority that realises what its notice will produce may withdraw it and serve another, and withdrawal before compliance leaves nothing behind.

Evidencing the resulting lawful position

The permission exists by operation of law, which means there is no decision notice to wave at a purchaser. Build the evidence file at the time:

1. The notice itself, with the plan, and proof of the date it took effect.
2. Dated photographs of the site before and after the works of compliance.
3. Invoices and contractor records showing what was done and when.
4. Any correspondence in which the authority acknowledges compliance.

Then apply for a Lawful Development Certificate under section 191 of the Town and Country Planning Act 1990 recording the existing use or operations as lawful. That converts an argument into a document, and it is what a lender or a purchaser's solicitor will want. Assembling the supporting documents for that certificate application is a smaller exercise than most owners expect, and doing it while the evidence is fresh is far easier than reconstructing it five years later. If you are weighing the cost of preparing those documents, PlanScope pricing sets out the options.

Enter your postcode on PlanScope to see which reports a site is likely to need if a fresh application follows.

This is general guidance, not legal advice. Check the position with your local planning authority or a qualified professional before relying on it. PlanScope provides AI-assisted draft reports for planning applications. Reports should be reviewed before submission. We do not guarantee planning approval.