Section 73B: varying a permission under the 2023 Act

Section 73B of the Town and Country Planning Act 1990, inserted by the Levelling-up and Regeneration Act 2023, allows a local planning authority to grant planning permission that alters an existing permission, provided the effect of the new permission would not be substantially different from the effect of the one it varies. The change that matters is the reach: unlike section 73, the new power is not confined to conditions, so the description of development itself comes into play.

Before relying on it, check whether it is actually available to you. A section on the statute book is not the same as a section in force, and the new power needs the relevant provision to be brought into force together with secondary legislation setting the application procedure and the fee. Verify the current position on legislation.gov.uk and against the authority's own application forms rather than assuming, because the answer determines whether you have three routes or two.

What the new power adds

The existing toolkit has a gap, and practitioners have worked around it for years.

Section 96A deals with non-material amendments and cannot touch the description of development. Section 73 allows permission to be granted without complying with conditions, which in practice means varying or removing conditions, and the Court of Appeal in Finney v Welsh Ministers confirmed that it cannot be used to grant something that conflicts with the operative part of the permission. So a scheme whose description said "erection of 24 dwellings" could not become 26 dwellings by condition variation, however modest the change looked.

That left a full fresh application as the only route for a change that was more than non-material but less than a new scheme. Section 73B is aimed squarely at that space.

The substantially different effect test

The test asks about effect, not about scale of drafting change. A one word amendment to a description can have a large effect, and a long list of condition changes can have almost none.

As a new statutory formula it has no settled judicial interpretation, so the sensible working approach is to read it against the existing case law on the limits of section 73. The courts have consistently refused to allow condition variation to produce a radically altered development, and they have treated conflict with the operative part as fatal. Section 73B removes the second of those obstacles but keeps a version of the first, pitched as a comparison of effects.

Practically, that means the application has to be argued, not asserted. Set out the effect of the existing permission and the effect of the proposed permission, side by side, across the matters the original decision turned on: scale, layout, appearance, access, residential amenity, highway capacity, drainage, heritage and ecology. Then explain why the difference is not substantial.

The comparison is also where the threshold judgements familiar from other parts of the system become useful, since the reasoning about materiality in de minimis in planning judgments covers similar ground from a different angle.

How it differs from section 73 in practice

Three differences are worth planning around.

The first is description. Section 73B lets you propose a changed description, which section 73 does not, and that is the whole reason most practitioners will reach for it.

The second is the condition set. A new permission under either route can carry a fresh set of conditions, and an authority is entitled to revisit them. That is a risk as well as an opportunity, because conditions that were negotiated down three years ago may come back in their original form. Go through the existing conditions line by line and say in the application which should be carried forward unchanged.

The third is what happens to everything hanging off the original permission. Approvals already granted under conditions do not automatically attach to a new permission, so the discharge position needs restating, and the practical mechanics of that are the same as for any new consent, as covered in approval of details or discharge of conditions.

Conditions, obligations and the paperwork around the permission

A varied permission usually needs a varied section 106 agreement. Obligations are tied to the permission they were given for, and a deed of variation or a fresh agreement is normally required so that the obligations bind the new permission as well. Raise it with the authority's legal team early, because a deed of variation can take longer than the application.

Where the original permission was for development subject to environmental impact assessment, a variation can require further environmental information and, depending on the change, a fresh screening opinion. The question is whether the environmental effects of the altered scheme were assessed, which is not the same question as whether the planning effects are substantially different. The scope of that obligation is set out in environmental information under the EIA Regulations.

Community Infrastructure Levy liability is recalculated against the new permission, and a change in floorspace can change the charge even where the planning effect is modest.

Description of development and its limits

The operative part is now variable, but it is not unlimited. Two constraints apply in practice.

A description cannot be rewritten so that a different development is permitted, because that would be a substantially different effect by definition. And a description cannot be used to smuggle in matters that were outside the original application altogether, such as additional land, since nothing in the power extends the application site.

Where the original permission was an outline consent, the interaction with reserved matters needs thought. Varying an outline description can affect what remains to be approved, and the limits on what can be left for later are set out in what cannot be reserved for later approval.

Choosing between the available routes

Illustrative example, not a real case: a permission for 42 dwellings is built out to plot 30 when the housebuilder wants to substitute a different house type on the remaining 12 plots, increasing the total floorspace by about 4 per cent, moving two plots by 1.5 metres and changing the materials on one terrace. Under section 96A the materials and the plot shifts might go through, and the floorspace change probably would not. Section 73 could handle the approved drawings condition but not any change to the description. Section 73B, where available, allows the whole package in one application with a single effects comparison.

The decision tree is short.

1. If the change is plainly trivial and does not touch the description, use section 96A.
2. If the change can be delivered by varying a condition without conflicting with the operative part, use section 73.
3. If the description has to change but the effect is not substantially different, use section 73B where it is in force.
4. If the effect is substantially different, or if the certainty of a clean consent matters more than speed, make a fresh application.

But do not choose on cost alone. A refused section 73B application leaves you with the original permission and a lost programme, and on a site where the original consent is approaching its time limit that can be an expensive way to save a fee. Whether the new power can be used to alter the time limit condition itself is a point to check against the section as enacted, since section 73 expressly cannot be used for that purpose.

If you are preparing the supporting documents for a variation, the report types by category index is a reasonable way to work out which of the original submissions need updating rather than reissuing.

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.