Section 73B: the new power to vary a planning permission
The 2023 Act inserted a power to vary a permission, including its description, where the effect is not substantially different. How to choose between the routes.
Section 73B of the Town and Country Planning Act 1990, inserted by the Levelling-up and Regeneration Act 2023, lets an applicant seek permission for development already permitted, with modifications, provided the effect of the new permission would not be substantially different from the existing one. A section 73B vary permission application is the route the profession has wanted for twenty years, because it bridges the gap between a non-material amendment and a fresh application.
As at 9 October 2026, check the position on legislation.gov.uk and in the Planning Practice Guidance before advising a client, because the power depends on procedural regulations and a fee being in place. Do not assume it is available in your authority until you have confirmed it.
The gap section 73 left
Section 73 allows an application to develop land without complying with a condition previously imposed. It creates a new permission, it does not require the original to be re-examined in full, and it has carried the industry's amendment work for decades.
Its limits are well established. Section 73 operates on conditions, so it cannot change the description of development, and the Court of Appeal confirmed in Finney v Welsh Ministers that a section 73 permission cannot be granted where the varied condition would conflict with the operative description. Section 73(5) prevents its use to extend the time limit for implementation. And a condition cannot be varied in a way that changes the development into something else.
Section 96A sits at the other end. It permits a non-material amendment, decided quickly, with no publicity requirement and no new permission created, because the original is amended. It also has no right of appeal against refusal, so a refusal leaves judicial review as the only challenge.
Between the two sat a real gap. A change that is more than non-material, but which touches the description of development, had no home other than a fresh application with everything reopened. The practical consequence was the drop-in permission, and the Supreme Court's decision in Hillside Parks Ltd v Snowdonia National Park Authority in 2022 made the risks of overlapping incompatible permissions very plain.
What the new power is intended to allow
Section 73B allows an application for planning permission for development that has already been permitted, with modifications, and it is not limited to conditions. The modifications can reach the description.
Two features matter. The authority must limit its consideration to the difference between the existing permission and the proposal, rather than redetermining the whole scheme. And the result is a new permission in its own right, which sits alongside the original rather than amending it.
That combination is what the profession asked for. A scheme that has moved on in detail, where the massing is the same but the unit mix or the description no longer matches, can be regularised without reopening the principle of development, the affordable housing position or the policy background.
The substantially different test
The statutory wording asks whether the effect of the new permission would be substantially different from the effect of the existing one. That is a test about effect, not about the extent of the drawing changes.
Expect the argument to run on the same ground that materiality arguments always run on. Scale and massing, the numbers of units and the mix, parking provision, access arrangements, the character of the use, and any change in the pattern of effects on neighbours, highways, drainage or heritage assets.
What makes a case stronger is a comparison document that puts the two permissions side by side and shows the difference in each topic, with a short statement of why the effect is not substantially different in each. What makes it weaker is a bundle of revised drawings with a covering letter.
Until a body of decisions and appeal outcomes builds up, nobody can tell you where the line falls. That is the honest position, and it is worth saying to a client who wants certainty. Early engagement with the case officer on whether the route is available for a particular change is time well spent.
Choosing between the available routes
The four routes do different jobs, and the choice is usually clear once you know which element is changing.
| Route | What it can change | New permission created | Appeal right |
|---|---|---|---|
| Section 96A | Non-material amendments only, including conditions | No, the original is amended | No |
| Section 73 | Conditions, but not the description | Yes | Yes, under section 78 |
| Section 73B | Conditions and the description, where the effect is not substantially different | Yes | Yes, under section 78 |
| Fresh application | Anything | Yes | Yes, under section 78 |
Four practical factors cut across the table. First, whether the description of development has to change, which eliminates section 73 immediately. Second, whether you can afford to have the principle of development reopened, which eliminates a fresh application on a site where policy has moved against you. Third, the levy position, because a new permission can trigger a recalculation of community infrastructure levy liability and the relief and exemption position has to be re-established. Fourth, the time limits, because the implementation clock on a new permission needs checking against the original.
Biodiversity net gain deserves its own check. Because a section 73B grant is a new permission, the deemed biodiversity gain condition can attach to it even where the original permission predated the regime, and our note on the deemed biodiversity gain condition explains when that bites. Together with the levy recalculation, these are the most common unforced errors on amendment applications.
Conditions and the permission you end up with
A permission granted under section 73B is a new permission, and the conditions on it have to be written out in full rather than cross-referenced to the original. That sounds administrative and it is not.
Three things to check on the decision notice. Whether every condition from the original has been carried across, because an omitted condition that the authority intended to keep will be noticed later. Whether conditions already discharged on the original have been re-imposed, which happens routinely and creates a second round of discharge applications for work already approved. And whether the time limit for implementation is expressed by reference to the original permission or afresh.
Where conditions have been discharged, ask the authority to word the new conditions so that the earlier approvals are treated as satisfying them. Most authorities will, if asked before the decision is issued.
Where this sits in the wider reform programme
Section 73B is one of a cluster of changes to the development management machinery in the 2023 Act, alongside the plan-making changes and the enforcement provisions. Several of those provisions came onto the statute book with their start dates left to secondary legislation, and the sequence has not been uniform.
That makes a habit worth forming. Before you rely on any provision of that Act, check whether it is in force for England, check whether the procedural regulations exist, and record the date you checked. Our note on plan-making reform and what happens to emerging plans deals with the transitional questions on the plan-making side, and the timeline at planning law updates is the place to follow which provisions are in force.
For a client, the useful advice right now is practical rather than theoretical. Scope the change, identify which element forces which route, and keep a fresh application in reserve where the policy background is favourable. Where it is not, the case for using an amendment route is stronger and the comparison document becomes the most important thing you produce.
A clear planning statement comparing the two permissions topic by topic is what carries an amendment application. You can draft one on PlanScope from the Planning Statement page, structured to UK planning policy, then review it before submission. PlanScope provides AI-assisted draft reports for planning applications. Reports should be reviewed before submission. We do not guarantee planning approval.
This is general guidance, not legal advice. Check the position with your local planning authority or a qualified professional before relying on it.
Frequently asked questions
Can section 73 be used to change the description of development?
No. Section 73 operates on conditions, and the Court of Appeal confirmed in Finney v Welsh Ministers that a section 73 permission cannot be granted where the varied condition would conflict with the operative description. Section 73(5) also prevents its use to extend the implementation time limit. Those limits are what section 73B was inserted to address.
What does substantially different mean in section 73B?
The test asks whether the effect of the new permission would be substantially different from the effect of the existing one, so it is about effect rather than the extent of drawing changes. Expect arguments on scale, unit numbers and mix, parking, access, the character of the use and the pattern of effects on neighbours and infrastructure.
Is there a right of appeal against refusal of a section 73B application?
Yes. Because the application is for planning permission, a refusal attracts a section 78 appeal in the same way as any other application. That distinguishes it from section 96A, where a refusal of a non-material amendment carries no right of appeal and the only challenge is judicial review.
Does a new permission affect community infrastructure levy liability?
It can. A new permission may trigger a recalculation of liability, and any relief or exemption previously claimed has to be re-established against the new permission. Start notices and assumption of liability also need revisiting. Check the levy position before choosing a route, because this is the most common unforced error on amendment applications.
What should I check on a section 73B decision notice?
Whether every condition from the original permission has been carried across, whether conditions already discharged have been re-imposed, and how the implementation time limit is expressed. Ask the authority before issue to word conditions so that earlier approvals satisfy them, which avoids a second round of discharge applications for work already approved.
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.