Section 73B: the new route for varying a permission
Section 73 cannot change the description of development. Section 73B was inserted to fill that gap, subject to a substantially different test and to being brought into force.
Section 73B of the Town and Country Planning Act 1990 was inserted by the Levelling-up and Regeneration Act 2023 to fix a specific problem: section 73 cannot be used to change the description of development. Section 73B can, subject to a test that the effect of the varied permission will not be substantially different from the existing one.
Before relying on any of this, check whether the provision is in force. As at 15 September 2026, verify the position on legislation.gov.uk, because section 73B was enacted subject to regulations and the section 73 practice described below continues to apply unless and until it is brought into force.
Why section 73 could not vary the description of development
Section 73 allows an application for permission to develop land without complying with conditions attached to an earlier permission. The local planning authority considers only the conditions, and grants a new permission with different conditions or refuses.
The limit was settled by the Court of Appeal in Finney v Welsh Ministers in 2019. A section 73 permission cannot be granted where the variation would conflict with the operative part of the original permission, meaning the description of the development itself. If the permission says "erection of a 100 metre turbine" and the applicant wants 125 metres, that is not a condition problem.
Two further limits are worth remembering. Section 73(5) prevents the section being used to extend the time limit for implementation. And the resulting permission is a new permission that stands alongside the original rather than replacing it, which matters for Community Infrastructure Levy liability and for working out which permission has been implemented.
The consequence was a gap. A change too large for a condition variation, but too small to justify a fresh application with a full evidence base, had nowhere sensible to go. The explainer on section 73 variations and the new permission they create covers that machinery in more depth.
What section 73B was inserted to do
Section 73B provides a route to apply for planning permission that varies or replaces an existing permission, including by altering the description of development.
Two features distinguish it. The authority considers the application in the light of the existing permission rather than starting from scratch, and it may grant only where it is satisfied that the effect of the new permission will not be substantially different from that of the existing one.
That framing is deliberate. It is meant to let a scheme evolve through detailed design and procurement without either a strained condition variation or a full reapplication.
The substantially different test
The statutory wording is the whole game, and it invites two questions.
Substantially different from what? The effect of the existing permission, which points at planning effects rather than at drawing differences. A change in the number of units, in height, in the amount of affordable housing, in trip generation or in the extent of harm to a heritage asset all go to effect.
Substantially different by what measure? There is no threshold in the section. It is a matter of planning judgement for the authority, which means the same change may be accepted by one council and refused by another until the practice settles.
Expect the early years to be uncertain, and expect authorities to be cautious. Where the change is finely balanced, a pre-application discussion is worth more than a clever statement.
How it interacts with non-material amendments
Three routes will coexist, and choosing between them is the practical skill.
| Route | What it can do | Typical use |
|---|---|---|
| Section 96A | Non-material amendment, including minor changes to conditions and wording | Small drawing corrections, a changed window position |
| Section 73 | Vary or remove conditions, but not the description of development | Amended plans conditions, revised phasing, changed hours |
| Section 73B | Vary or replace a permission, including the description, where the effect is not substantially different | Unit mix changes, a modest increase in floorspace, a changed description |
Section 96A remains the fastest and least expensive route, decided without the publicity that attends a planning application, and it is limited to changes that are not material. Section 73 remains the workhorse for condition variations where the description stays intact.
What to check on the statutory position
Provisions in the 2023 Act have been brought into force in stages, and some await regulations before they operate. Check the section's status directly rather than relying on a summary, including this one, and check whether any accompanying procedure regulations and fee provisions have been made.
Where the position is unclear, the safe course is to proceed under the existing route that definitely works and to raise the alternative with the authority. The planning law updates timeline is a place to follow this kind of reform, and the primary source is always the legislation itself.
Choosing between the three routes
Work through it in this order.
- Can the change be made without touching the description, purely by varying a condition, including an approved plans condition? If yes, section 73 is the route.
- Is the change so slight that it is not material at all? If yes, section 96A is quicker and cheaper.
- Does the change alter the description, or go beyond what a condition variation can carry, while leaving the planning effects broadly as they were? That is section 73B territory, assuming it is in force.
- Does the change alter the planning effects substantially, or does the original permission carry an obligation that no longer fits? Then it is a fresh application, and pretending otherwise will cost more time than it saves.
Obligations deserve their own thought. A section 106 agreement tied to a specific permission does not automatically attach to a new one, so a deed of variation or a fresh agreement is usually needed whichever route you take.
Time limits are the other trap. Neither route revives a permission that has expired, and neither extends the period for implementation. Where a permission is approaching its deadline, implementing it lawfully first and varying afterwards is a different exercise from varying a permission that has not started, and the order matters.
There is also the question of what happens to the original permission. It survives, which means two permissions exist for the same land, and the developer has to be clear about which one is being built out. Officers will ask, and a statement that does not answer it invites a condition attempting to tie the two together.
Drafting the application so the scope is clear
Whatever the route, the drafting problem is the same. Make it impossible to misunderstand what is changing.
Identify the existing permission by reference and date. List every document and drawing being superseded, with the replacement reference against it. Provide a schedule of changes with a column for the planning effect of each. State expressly what is not changing, including any obligations, and say what the applicant proposes should happen to the original permission.
A Planning Statement built around that schedule does most of the work, and it is the document an officer will lift from when writing the report. Keep the schedule at the front rather than in an appendix, because a reader who has to hunt for the comparison will assume there is a reason it is hidden.
Publicity is worth planning for as well. A variation application is publicised like any other, and neighbours who accepted the original scheme will read the new description rather than the schedule. A covering note explaining plainly what is changing, in the words a neighbour would use, prevents a lot of objections built on a misreading. Where the change touches a matter that was contested first time round, address it directly instead of hoping nobody notices. The explainer on section 73 and varying a condition without starting again shows how narrow the scope of a variation application can be kept when the paperwork is precise.
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.
Frequently asked questions
Why can section 73 not change the description of development?
Because the Court of Appeal held in Finney v Welsh Ministers that a section 73 permission cannot conflict with the operative part of the original permission. Section 73 deals only with the conditions attached to a permission. Where the change would contradict the description of development itself, the application falls outside the section.
What is the test under section 73B?
The authority may grant permission only if satisfied that the effect of the new permission will not be substantially different from that of the existing one. The comparison is with planning effects rather than with drawing differences, and there is no numerical threshold, so it is a matter of planning judgement for the authority.
Is section 73B in force?
Check the current position on legislation.gov.uk before relying on it. Provisions of the Levelling-up and Regeneration Act 2023 have been brought into force in stages and some await regulations. Where the status is unclear, proceed under the route that definitely operates and raise the alternative with the authority.
When should I use section 96A instead?
Where the change is not material at all. Non-material amendments are decided without the publicity attached to a planning application, are faster and cost less, and can cover small drawing corrections or a changed window position. There is no statutory definition of non-material, so the authority decides in each case.
Does a section 106 agreement carry over to a varied permission?
Not automatically. An obligation tied to a specific permission does not attach itself to a new one created by a variation, so a deed of variation or a fresh agreement is usually required. The same point applies to Community Infrastructure Levy liability, which is recalculated against the new permission subject to the abatement provisions.
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.