Section 73 refusals and the fundamental alteration limit
Two of the three grounds for refusing a section 73 application are jurisdictional. Here is how to keep a variation inside the limits and what to do when it falls outside.
A section 73 application is refused for one of three reasons: the variation conflicts with the description of development, the change is so large that it goes beyond what section 73 can do, or the varied condition fails on its planning merits. Only the third is a normal planning argument. The first two are jurisdictional, and an appeal against a section 73 refused on those grounds is usually an uphill fight, because an inspector has no more power to grant the permission than the council did.
Section 73 of the Town and Country Planning Act 1990 lets an applicant seek permission for development without complying with a condition attached to an earlier permission. The authority may only consider the question of the conditions.
What section 73 can and cannot change
It can remove a condition, replace a condition with a differently worded one, or substitute a new approved drawing where the original permission secured the drawings by condition. That last point is the whole basis of the minor material amendment practice, because almost every modern permission lists its approved plans in a condition.
It cannot extend the time limit for implementation. Section 73(5) says so directly, and an application seeking to do that will be refused whatever its merits.
It cannot be used where the permission has already expired. A section 73 varies a live permission, so if the original has lapsed there is nothing to vary and a fresh application is the only route.
And it does not amend the original. Section 73 produces a new permission which sits alongside the earlier one, carrying its own conditions and its own reference number.
Why the description of development constrains everything
The decisive case is Finney, in which the Court of Appeal held that a section 73 permission cannot be granted where the variation would conflict with the description of development in the original permission. The description defines the development for which permission was granted, and section 73 does not reach it.
The practical consequences are sharp. A permission described as the erection of two wind turbines with a tip height of 100 metres cannot be varied under section 73 to give a tip height of 125 metres, because the description says otherwise. A permission for the erection of 24 dwellings cannot become 26 dwellings. A permission described by reference to a specific drawing number cannot depart from that drawing.
Read the description on the decision notice before anything else, word by word. Where it contains numbers, dimensions or a drawing reference, those figures are fixed for section 73 purposes, and a variation touching them needs a fresh application.
The fundamental alteration objection
Even where the description is silent, section 73 has a limit. The courts have consistently held that it cannot be used to make a change amounting to a fundamental alteration of the permission, because at that point the applicant is seeking a different development rather than the same development on different conditions.
There is no numerical test. The question is one of fact and degree, and the factors that come up repeatedly are the scale of the change relative to the whole, whether it alters the nature or the purpose of the development, whether it affects matters that were central to the original decision, and whether it would require assessment of issues the original application never addressed.
A change of external materials on one elevation is not fundamental. Re planning an approved block to move a stair core and add a floor almost always is. Between those two there is a wide grey area, and both officers and inspectors decide it case by case.
The practical signal to watch for is consultation. If the change is large enough that the highway authority, the lead local flood authority or the Environment Agency would need to reconsider its original response, expect the fundamental alteration argument to be raised.
Evidence that the change is not fundamental
Build the case into the application rather than answering it after the officer objects. Four things do the work.
First, a comparison schedule: the approved figure and the proposed figure for floorspace, unit numbers, heights, footprint, parking and any other quantified parameter, with the percentage change. Numbers close the argument faster than adjectives.
Second, a drawing overlay showing the approved and proposed layouts on the same base, so the officer can see what moved.
Third, a statement of what has not changed, covering the use, the access, the unit mix, the drainage strategy and the parameters each consultee assessed. The absence of change is as relevant as its presence.
Fourth, a short note on each original reason for approval and each consultee response, confirming that the change does not disturb it. Where a consultee would need to comment again, say so and provide the updated information rather than hoping nobody notices.
Set all of this out in the Planning Statement accompanying the application. A section 73 statement that opens with the description of development, quotes it, and then explains why the proposal is consistent with it is doing the right work in the right order.
The fresh application alternative and its cost
Where the change is fundamental or conflicts with the description, a fresh full application is the honest answer. It costs a full fee, a full consultation period, and it reopens the whole scheme rather than the single point you wanted to change.
That last risk is the one clients underestimate. A new application is determined against the policy position on the date of decision, not on the date of the original permission. If the local plan has moved on, if biodiversity net gain now applies, or if the authority's housing land supply position has changed, the fresh application may not be granted on the same terms.
Where the original permission is still live, keep it alive. Implement it if you can, and run the new application in parallel rather than surrendering the consent you already hold. The interaction between parallel permissions is a separate question with its own traps.
The Levelling-up and Regeneration Act 2023 inserted section 73B, a wider route intended to allow variations, including to the description, where the result is not substantially different from the existing permission. Check whether that provision and its supporting procedural rules are in force before relying on it, and confirm the position with the authority in writing, because commencement of the 2023 Act has been staged over several years.
Drafting the description to keep section 73 available
Most section 73 problems are created at the original application, by a description that is more specific than it needed to be.
Write the description as the minimum necessary to define the development. The erection of 24 dwellings with associated access, parking and landscaping is a workable description. The erection of 24 dwellings comprising 12 houses and 12 flats over three storeys with 48 parking spaces, in accordance with drawing 1234 revision P03, is a description that has fixed four separate parameters and removed most of the flexibility you will want in two years.
Where an officer proposes to add detail to the description during the application, push back politely and offer a condition instead. A parameter secured by condition can be varied under section 73. The same parameter written into the description cannot.
Keep the approved plans in a condition rather than in the description, check the decision notice on issue, and ask for a correction under section 96A or by amendment if the description as issued is not what was applied for.
If a section 73 has been refused, weigh the appeal against the resubmission on the jurisdictional point rather than the planning merits, as our notes on the limits of varying conditions and on choosing between resubmission and appeal both set out.
This is general guidance, not legal advice. Check the position with a qualified professional before relying on it. If a fresh application is the answer and the supporting documents need rebuilding, enter your postcode on PlanScope to see what the scheme now needs. PlanScope provides AI-assisted draft reports for planning applications. Reports should be reviewed before submission. We do not guarantee planning approval.
Frequently asked questions
Can section 73 be used to change the description of development?
No. Following the Court of Appeal decision in Finney, a section 73 permission cannot be granted where the variation would conflict with the description of development in the original permission. If the description fixes a height, a unit number or a drawing reference, that figure cannot be varied by section 73 and a fresh application is required.
What counts as a fundamental alteration?
There is no numerical test. Courts and inspectors weigh the scale of the change against the whole, whether it alters the nature or purpose of the development, whether it disturbs matters central to the original decision, and whether it raises issues the original application never assessed. A material change that would make consultees reconsider is the usual warning sign.
Can section 73 extend the time limit for implementation?
No. Section 73(5) rules it out directly, so an application seeking to extend the commencement period will be refused whatever its planning merits. Section 73 also cannot be used once the original permission has expired, because there is no live permission left to vary. A fresh application is the only route in both cases.
Does a section 73 permission replace the original?
No. It creates a new planning permission that sits alongside the original, with its own reference, conditions and approved drawings. Both remain on the register. Ask the authority to consolidate the conditions into the new decision notice rather than cross referring, because a chain of variations quickly becomes hard for anyone else to read.
How should the description of development be drafted?
As the minimum needed to define the development. Avoid writing unit mixes, storey heights, parking numbers or drawing references into it, because each figure fixed there is a figure section 73 cannot vary later. Secure those parameters by condition instead, and check the decision notice on issue to confirm the description matches the application.
Sources and further reading
This article is general guidance about the planning system in England and, where stated, the rest of the UK. It is not legal or professional advice. Check your local planning authority’s validation requirements and take professional advice for your specific site.