Section 73B applications to vary a permission

Section 73B of the Town and Country Planning Act 1990 allows a local planning authority to grant permission for development that is not substantially different from development already permitted, and it can reach parts of a permission that section 73 cannot touch, including the description of development itself. A section 73B application is the route for a change that is more than non-material but falls short of a fresh scheme.

The provision was inserted by the Levelling-up and Regeneration Act 2023. Check on legislation.gov.uk whether it is in force and whether the procedural regulations and the application fee have been made before relying on it, because the power depends on secondary legislation for the machinery around it. Where it is not yet available, the existing routes are what you have.

The gap section 73B was written to fill

Section 73 permits an application for development without complying with a condition attached to an earlier permission. That is all it does. It works on conditions, and the courts have held that it cannot be used to vary a condition in a way that conflicts with the operative part of the permission, because the description of development is not a condition and cannot be rewritten through the back door.

So a permission for 42 dwellings that becomes 44 dwellings cannot be varied under section 73, even if every substantive judgment is unaffected, because the number appears in the description. The practical consequence has been a full fresh application for a change that nobody disputes, with the consultation, the fee and the delay that implies.

Section 73B addresses that by asking a different question. Not whether a condition can be relaxed, but whether the development as varied would be substantially different from what was permitted.

The substantially different test in practice

The statutory test is comparative and it looks at the development, not at the acceptability of the change. Two propositions follow.

A change can be large in cost or in engineering terms and still not be substantially different, because the comparison is with the permitted development rather than with a blank site. And a change can be small in area and still be substantially different, if it alters the nature of what was permitted, for example by introducing a use the permission did not include.

Factors that bear on it in practice include the scale of the change relative to the permitted scheme, whether the change affects matters that were central to the original decision, whether it introduces effects that were not assessed, and whether the description of development would still fairly describe what is proposed. An additional storey on a two storey building is likely to be substantially different. A 300 mm increase in ridge height across a 60 unit scheme is not.

The honest uncertainty here is where the line falls, and it will be worked out through authority practice and appeal decisions rather than by reasoning from the words alone. Treat early decisions as indicative of how the test is being approached rather than as settled law.

How it differs from section 73 and section 96A

The third column distinction matters for reasons beyond procedure. Section 96A amends the original permission, so there is one permission on the file. Section 73 and section 73B both produce a new, freestanding permission sitting alongside the original, which means two live permissions and a decision at some point about which is implemented.

Keep a note on the file recording which permission the development is being built under, because a site with an original permission, two section 73 permissions and a section 73B permission is a title report problem waiting to happen.

What the authority considers

The authority's consideration is directed at the difference between the proposal and the existing permission, and it must have regard to that existing permission including its conditions. The original grant is the baseline, so matters settled by it are not reopened.

That is the attraction and it is also the limit. A section 73B application is not an opportunity to revisit a condition unrelated to the change, and an authority is not obliged to reconsider the principle of development. Equally, an applicant cannot use it to avoid a consequence the change does in fact produce. If the variation creates a daylight effect that was not assessed, that effect is part of the difference and it will be assessed.

Two things to check before assuming the change is straightforward.

• Environmental impact assessment. A varied scheme may need fresh screening, and where the original was EIA development the change has to be considered against the environmental statement.
• Biodiversity net gain. The new permission may engage the biodiversity gain condition even where the original predated the regime, depending on the transitional provisions. That is a question to resolve with the authority before applying, and the position for smaller schemes is set out in the note on biodiversity net gain for small sites.

Drafting the application

Make the difference easy to see. The authority is being asked a comparative question, so give it a comparison.

1. State the existing permission reference, its date and its description of development in full.
2. Give the proposed description of development, with the changed words marked.
3. Provide a schedule of differences: each change, the drawing or condition it affects, and a sentence on why it is not substantially different.
4. Provide a plans list showing superseded drawings against replacement drawings, with revision numbers.
5. Provide a draft schedule of conditions for the new permission, marked to show which are carried across unchanged, which are amended and which fall away.
6. Address the effects of the difference, and only those effects, in the supporting statement.

The plans list is the part that causes most trouble later. A new permission needs its own complete list of approved drawings, and a list that refers to drawings approved under the original permission by revision numbers that have since moved produces a discharge of conditions dispute two years on. Rebuild the list in full.

Conditions on the new permission

Because section 73B produces a new permission, it carries a full set of conditions rather than an amendment to the old ones. Re-impose the original conditions with any necessary updating, and pay attention to the time limit condition and to any condition whose trigger has already passed.

A condition requiring approval of materials before above-ground work, on a scheme where the materials were approved under the original permission, should be reworded to refer to the earlier approval rather than requiring the process to be repeated. Authorities usually accept that if you draft it for them.

Set the whole argument out in a Planning Statement structured around the difference rather than around the scheme, and follow developments in this area through the planning law timeline. The wider reforms introduced by the same Act, including the changes to plan making, are covered in the note on local plan reform under the 2023 Act.

Enter your postcode on PlanScope to see which supporting documents a variation application is likely to need.

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.