Section 73B: the minor variation route explained

Section 73B of the Town and Country Planning Act 1990 was inserted by the Levelling-up and Regeneration Act 2023 to let an authority grant a varied planning permission where the effect of the change is not substantially different from the permission being varied. Unlike section 73, it can reach the description of development, which is the limitation that has caused most of the trouble with post-permission changes for the last several years.

As at the time of writing, the 2023 Act has been brought into force in stages and the position on section 73B should be verified against the current text on legislation.gov.uk and the regulations bringing it into force before you rely on it. What follows explains what the provision does and how it sits alongside the routes that already exist.

The problem it was written to solve

Section 73 allows an application to develop land without complying with a condition previously imposed. The authority considers only the condition, and if it grants, the result is a fresh permission alongside the original.

The difficulty is that section 73 cannot be used to grant something inconsistent with the operative part of the permission, meaning the description of development itself. The Court of Appeal confirmed the point in Finney v Welsh Ministers, and the practical result has been familiar to every agent since: a permission described as "erection of two dwellings" cannot become three by varying the approved plans condition, and a permission for a turbine of a stated height cannot be varied to a taller one.

Section 96A, the non-material amendment route, does not solve it either. It cannot change the description of development, "non-material" has no statutory definition, and the outcome is an amendment to the existing permission rather than a new one.

So schemes that had moved on in ordinary ways, a few extra units, a change in mix, a revised description that better matched what was being built, were pushed into full fresh applications with all the cost and delay that implies.

What section 73B does differently

Three features distinguish it.

It allows the varied permission to differ from the existing permission, including in the description of development, so long as the effect is not substantially different.

It produces a new permission rather than an amendment, which matters for implementation, for conditions and for anyone relying on the title.

It allows the authority to impose new conditions and to carry forward or omit existing ones, giving a route to tidy a permission that has accumulated poorly drafted conditions.

What it is not is a licence to rewrite a scheme. The substantially different test is a real constraint, and applications that stretch it will be refused or, worse, granted and then challenged.

One further difference from section 96A is worth noting for anyone drafting the application. Section 96A produces an amendment recorded against the original permission, so the original decision notice and the amendment have to be read together. Section 73B produces a standalone permission, which is easier to explain to a lender and easier to condition properly.

The "not substantially different" test

There is no statutory definition, and the meaning will be worked out through practice, appeals and eventually the courts.

Sensible working assumptions until then. The comparison is between the effect of the varied permission and the effect of the existing one, not between the varied permission and the development plan. Effect covers the planning consequences: scale, appearance, amenity, highways, drainage, heritage and the rest, not merely the numbers. A change that engages a different policy test, or that triggers a threshold the original did not, is unlikely to pass.

Practical examples of the sort of change that plausibly sits within it: a modest increase in floorspace with no change in unit numbers or massing, a revised description to match approved drawings, a change of materials palette recorded in the description, or a rationalisation of conditions.

Changes that plausibly sit outside it: crossing the ten-unit major development threshold, adding a storey, changing use class, or anything that would have required a different suite of technical reports at the outset.

Where the change is borderline, a fresh application is often the safer instrument, because a permission granted under a route that turns out to have been unavailable is vulnerable.

Expect authorities to be cautious in the first year or two of any new route. Officers who have been refused at appeal for stretching section 73 will not be quick to stretch its replacement, and a well-argued application that explains why the effect is not substantially different, point by point against the original approval, will do better than one that simply asserts it.

What a variation still cannot avoid

This is the part that catches people out on any post-permission route.

Environmental impact assessment screening applies to the varied proposal. A change that takes the scheme over a Schedule 2 threshold, or that alters the environmental effects, needs screening on its own terms.

Habitats Regulations assessment applies in the same way where a European site could be affected.

Biodiversity net gain has its own rules for varied and section 73 permissions, including how the pre-development baseline date is fixed. Check the current position carefully rather than assuming the original baseline survives, and expect to need a Biodiversity Net Gain Assessment reworked to the varied scheme where the footprint moves.

Community Infrastructure Levy liability is recalculated against the new permission, normally with credit for the earlier one, so a variation adding floorspace has a cost.

Nutrient neutrality and water neutrality obligations, where the site sits in an affected catchment, apply to the varied scheme as well, and a change in unit numbers or occupancy changes the calculation.

Section 106 obligations do not transfer automatically. A new permission needs the obligation to be applied to it, usually by a deed of variation, and forgetting this produces a permission that cannot lawfully be implemented on the terms everyone assumed.

Choosing the route

Two habits reduce how often any of this is needed. Draft the description of development at the outset in terms broad enough to accommodate ordinary development, without becoming so vague that the authority refuses to validate it. And negotiate conditions before the decision notice is issued rather than living with wording you will later pay to change. The policy case for either sits in the Planning Statement.

Reforms of this kind arrive in pieces, with the primary provision in one Act and the order bringing it into force in a statutory instrument months or years later. Following them through the planning law updates timeline is easier than reading the instruments cold, and the report index shows what a varied scheme may need to resubmit.

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.