Section 106 agreements for architects

What is a section 106 agreement?

A section 106 agreement is a legally binding planning obligation under section 106 of the Town and Country Planning Act 1990 that makes a development acceptable in planning terms by mitigating its impacts. It is made between a person with an interest in the land and the local planning authority, runs with the land, and secures things a planning condition cannot, such as affordable housing or financial contributions.

The S106 is often negotiated by planning consultants and lawyers. But many of its triggers and obligations land on the design and the programme, so the project team needs to know what it says and when each obligation bites.

Section 106(1) allows a planning obligation to do four things:

• restrict the development or use of the land in a specified way;
• require specified operations or activities to be carried out on, in, under or over the land;
• require the land to be used in a specified way;
• require a sum or sums of money to be paid to the authority, on specified dates or periodically.

Under s106(9), the obligation must be made by deed, state that it is a planning obligation for the purposes of section 106, identify the land, the person entering into it and their interest, and the enforcing authority. It is registered as a local land charge (s106(11)) and binds successors in title (s106(3)). Authorities can enforce by injunction and, after at least 21 days' notice, enter the land to carry out required works and recover the cost (s106(5)–(7)).

Agreement or unilateral undertaking?

An obligation can be a bilateral or multi-party agreement, or a unilateral undertaking given by the landowner alone. A unilateral undertaking cannot bind the authority, because the authority is not a party to it, which is why it is common at appeal and for simple payments.

Anyone with a legal interest in the land must normally be a party so the obligations bind the land. That usually means the freeholder, any long leaseholders and any mortgagee, alongside the authority. Architects are not parties, although they may be named in clauses that secure design quality or retention.

The three legal tests for a planning obligation

Regulation 122(2) of the Community Infrastructure Levy Regulations 2010 says an obligation can only be a reason for granting permission if it passes all three tests. Government guidance confirms they apply whether or not the authority charges CIL.

What section 106 agreements typically include

Contents vary by scheme and local policy, but six families of obligation come up again and again. Most of them reach into the design or the programme.

Affordable housing obligations should only be sought for major residential development, defined in national guidance as 10 or more homes or a site of 0.5 hectares or more, and not for residential annexes or extensions. Smaller schemes may still need an obligation for a specific impact, such as a car-free restriction or a habitat mitigation payment, depending on local policy.

How section 106 differs from CIL

The Community Infrastructure Levy is a fixed, non-negotiable charge per square metre of new floorspace, set in a charging schedule the authority has chosen to adopt. A section 106 obligation is negotiated, site-specific and tied to the impacts of that scheme.

CIL is optional for authorities, so not every area charges it. It usually applies to development creating 100 square metres or more of net additional floorspace, or any new dwelling regardless of size, and becomes payable when development commences unless liability has been assumed and a payment window applies. In London, the Mayoral CIL is charged in addition to borough CIL.

Any authority that receives either must publish an annual infrastructure funding statement by 31 December, which is a useful public record of what has been collected and spent. The CIL guidance on GOV.UK was updated in June 2026, so check the current text rather than older summaries.

How obligations and planning conditions interact

Conditions come first. Where an impact can be addressed by a condition, a condition should be used rather than an obligation, and conditions cannot require payments of money, which is why financial contributions sit in the S106.

The National Planning Policy Framework published on 17 August 2026 restates this in policy DM6, which also says national model conditions and obligations should be used unless there are strong reasons not to. In practice the two documents work as a pair:

Commencement triggers

A pre-commencement condition and a "no development until" S106 clause can both block a start on site. Track both against the same programme.

Definitions

"Commencement" and "occupation" are defined in the deed and may not match how the conditions use the words. A material operation that lawfully implements the permission may still trigger a payment.

Variations

A section 73 application to vary conditions often needs a deed of variation or a new unilateral undertaking to carry the S106 across to the new permission.

Discharge evidence

An affordable housing scheme or travel plan may be required by both, and the authority will expect consistent information.

Changing an agreement after permission

An agreement can be changed by a deed of variation at any time if the parties agree. Without agreement, an application under section 106A can be made once the obligation is five years old (or if it predates April 2010), on the basis that it no longer serves a useful purpose or would serve it equally well modified. Refusal or non-determination can be appealed under section 106B.

What is changing in 2026

The August 2026 NPPF introduces a "medium development" category (10 to 49 homes on sites up to 2.5 hectares), and the government has consulted on draft model S106 agreements and unilateral undertakings intended to become the default starting point for those schemes. Neither change alters the core section 106 framework in the 1990 Act.

What architects should track in a section 106 agreement

The architect is rarely a party to the deed, but the practice is often the first to notice when a design change or programme slip collides with an obligation. A simple register catches that early.

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  Each obligation and its trigger: commencement, a percentage of occupations, practical completion of a phase.
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  Design dependencies: affordable unit numbers, sizes, tenure locations, wheelchair units, parking caps, public realm areas.
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  Submissions owed: schemes, strategies or plans the authority must approve under the deed, with dates and approval status.
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  Linked conditions: the conditions that cover the same topic.
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  Change risk: any design change that could alter unit mix, floor areas or layout fixed by the deed, flagged before it reaches the client or contractor.
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  Novation and retention clauses: some agreements secure the original architect or design quality reviews, which affects appointments.

When a dispute arises over whether a trigger was met, contemporaneous evidence is what settles it.

Keep a dated record of who confirmed each item. Unmet triggers can also delay sales or occupation, because buyers' solicitors will check S106 compliance.

Where Avoice fits

Conditions and S106 obligations are usually tracked in separate spreadsheets by separate people, which is exactly where overlapping triggers get missed.

The Planning Conditions tracker in Avoice's Compliance module records both conditions and S106 obligations in one register, with triggers, owners, submissions and approval status against the project programme. Evidence links back to the dated Project Record, so the team can see what was submitted and when.

Software can record, link and flag. The planning consultant, the lawyers and the authority still decide what the deed requires and whether a trigger has been met.