Planning permission is not always final. Once a decision has been granted, circumstances change, designs are refined, and site conditions reveal complications that require adjustments. Section 73 of the Town and Country Planning Act 1990 provides a mechanism to vary or remove conditions attached to an existing planning permission without having to submit a full new application. Crown Architecture & Structural Engineering Ltd regularly assists clients with Section 73 applications to modify conditions and keep projects on track. This guide explains when and how to use the Section 73 route.

What is a Section 73 Application?

A Section 73 application is a statutory application to modify or remove one or more conditions attached to an existing planning permission. It is commonly used to:

• Amend approved drawings (often described as a “minor material amendment”)
• Alter a pre-commencement condition (e.g. to change the approved materials or landscaping scheme)
• Remove a condition that has become redundant or disproportionate
• Vary a condition that restricts hours of operation, delivery times, or occupancy

If approved, a Section 73 application creates a new planning permission — a distinct consent that sits alongside (not replaces) the original permission. Both permissions remain extant.

Section 73 vs Other Amendment Routes

It is important to choose the right amendment route. There are three options:

Non-Material Amendment (Section 96A)

For changes that are genuinely minor and do not materially affect the development. Examples include small adjustments to window positions, minor changes to wall lengths, or alterations to internal layout that do not affect external appearance. This is a quicker, cheaper process with a statutory fee of £234 in England (as of 2025). However, the local planning authority (LPA) must be satisfied that the change is truly non-material.

Section 73 (Minor Material Amendment)

For changes that are more significant but still within the scope of the original permission. Typically used for changes to approved plans, alterations to materials, or amendments to conditions that are proportionate in scale and impact. Section 73 requires a new application and fee.

New Full Application

Where the proposed changes are so significant that they fundamentally alter the nature of the development — for example, increasing the footprint substantially, adding a storey, or changing the use — a full new planning application is needed.

What Section 73 Cannot Do

Case law has established important limits on Section 73:

• It cannot be used to modify the description of development in the original permission. If the permission is for “a single-storey rear extension,” a Section 73 cannot convert it into “a two-storey rear extension.”
• It cannot be used to extend the time limit on a planning permission (there are separate provisions for this).
• It cannot vary conditions that have already been discharged or conditions that are integral to the grant of permission itself (as opposed to conditions attached to it).
• It cannot make changes that would render the development materially different from what was originally approved.

The courts have confirmed (in cases such as R (Vue Entertainment) v City of York Council) that a Section 73 consent must remain consistent with the operative part of the original permission. The LPA cannot grant a Section 73 permission that fundamentally changes the development.

Common Uses in Residential Projects

In residential architecture and structural engineering, Section 73 applications most commonly arise in these scenarios:

Amended Architectural Drawings

Design refinements during detailed design or construction may produce drawings that differ from those originally approved. Where changes are more than minor (e.g. alterations to the roof line, revised window sizes, changes to the footprint within the limits of the permission), a Section 73 is used to substitute the amended drawings for those approved under the original condition.

Materials Changes

A condition requiring approval of materials in writing before work commences (a “pre-commencement condition”) can be addressed by either a pre-commencement discharge application or, if the proposed materials differ from those described at application stage, by a Section 73 to vary the condition itself.

Structural Changes Driven by Site Conditions

When foundation investigations reveal unexpected conditions requiring a structural redesign that alters the external envelope, a Section 73 may be needed to regularise the revised design.

Developer Changes Post-Purchase

A developer purchasing a site with existing planning permission may want to substitute their preferred house type or layout. Where changes are within the scope of the original consent, Section 73 is the appropriate mechanism.

The Section 73 Application Process

Step 1: Identify the Condition to Be Varied

Your application must identify the specific condition(s) you want to vary or remove, and explain what you want to replace them with.

Step 2: Prepare Supporting Documents

Depending on what you are varying, supporting documents may include:

• Revised architectural drawings
• Design and access statement addendum explaining the changes and why they are needed
• Updated structural information if the changes have structural implications
• Heritage impact assessment if the site is in a conservation area or involves a listed building

Step 3: Submit via the Planning Portal

Section 73 applications are submitted on the standard planning application form. In England, the application fee in 2025 is the same as the original application fee category, so for a householder application it is £258.

Step 4: Determination

The LPA has 8 weeks to determine a Section 73 householder application (13 weeks for major applications). The application is assessed by a planning officer who considers whether the proposed changes are within the scope of the original consent and whether they raise any new planning issues. Consultation requirements depend on the nature of the changes.

Step 5: Decision

If approved, the LPA issues a new planning permission incorporating the amended condition(s). If refused, the applicant can appeal under the same process as any other planning refusal.

Relationship Between Section 73 and Building Regulations

Planning permission and Building Regulations are separate consents. A Section 73 approval amends your planning position but does not automatically update your Building Regulations application. If the Section 73 changes affect matters covered by Building Regulations (e.g. structure, drainage, insulation), a revised Building Regulations submission will also be required. Ensure both consents are aligned before proceeding on site.

Costs

• Planning Portal application fee: £258 (householder, England, 2025)
• Architect’s fees for preparing revised drawings and statement: £500–£2,000 depending on complexity
• Structural engineer’s fee if structural drawings are revised: £500–£1,500
• Total professional fees: £1,500–£4,000 for a typical residential Section 73

How Crown Can Help

Crown Architecture & Structural Engineering Ltd prepares Section 73 applications for residential and commercial clients. We assess whether your proposed changes fall within the Section 73 route or require a fresh application, prepare the necessary drawings and documents, and submit and manage the application on your behalf. Call us on 07443804841 to discuss your amendment needs.

Frequently Asked Questions

How long does a Section 73 application take?

The statutory determination period for a householder Section 73 application is 8 weeks from valid registration. In practice, many LPAs process straightforward Section 73 applications within 6–8 weeks; complex cases may take longer.

Can I start work before my Section 73 is approved?

You can continue work under the original planning permission while a Section 73 is pending, provided the works being carried out comply with the original consent. You cannot implement the proposed changes until the Section 73 is approved. Starting work on the amended design before approval may constitute a breach of planning control.

Does a Section 73 restart the 3-year implementation period?

Yes. A Section 73 creates a new planning permission with its own 3-year time limit for implementation (unless the LPA specifies otherwise). This can be advantageous if the original permission is approaching expiry.

What happens to the original planning permission after a Section 73 is granted?

Both permissions remain valid. The applicant may choose to implement either one. In practice, if the Section 73 has been obtained to regularise changes already made on site, it is the new consent that governs the as-built position.

Can I use Section 73 to change the approved external materials?

Yes, in many cases. If there is a condition specifying materials, a Section 73 application can seek to vary that condition to approve different materials. The LPA will assess whether the proposed materials are acceptable in planning terms.

What is the difference between Section 73 and Section 73A?

Section 73 applies to development that has not yet commenced or is in progress. Section 73A (also known as a “retrospective” application) is used to regularise development that has already been carried out without, or not in accordance with, planning permission. Both create a new planning permission if approved.

My planning permission has expired — can Section 73 help?

No. Section 73 can only vary conditions on an extant (live) planning permission. Once a permission has expired without implementation, a fresh application is needed. If the permission is close to expiry, a Section 73 application (if approved) creates a new permission with a fresh time limit.