S106 Unilateral Undertakings: When Developers Self-Submit Planning Obligations

Most Section 106 agreements are bilateral — signed by the developer (and any other bound parties) and the local planning authority. But the Town and Country Planning Act 1990 also provides for unilateral undertakings: planning obligations entered into by the developer alone, without the council's signature.

Unilateral undertakings are a smaller, narrower tool than full bilateral S106 agreements — but on the right scheme, they can save weeks of negotiation and unlock a planning approval that would otherwise stall. This guide explains when they're used, what they can do, and what they can't.

This covers England only. This is general guidance, not legal advice. Always seek legal advice before drafting a unilateral undertaking.

The Statutory Basis

Section 106 of the Town and Country Planning Act 1990 provides at subsection (1) that any person interested in land in the area of a local planning authority may, "by agreement or otherwise", enter into a planning obligation. The "or otherwise" wording is what enables a developer to give a planning obligation as a unilateral commitment, without the council needing to be a counterparty to the document.

Whether bilateral or unilateral, every planning obligation must comply with the formal requirements set out in the rest of Section 106 — including subsection (9), which requires the obligation to be executed as a deed and to contain the matters that subsection prescribes.

Both forms are equally binding once executed. Both run with the land. Both can be enforced by the LPA. The substantive difference is whether the council has to sign.

You can read the legislation directly at Section 106 of the Town and Country Planning Act 1990.

When Developers Use Them

Appeal Schemes

The most common use of unilateral undertakings is on planning appeals. When an application has been refused by the LPA and the developer appeals to the Planning Inspectorate, the inspector may indicate that the appeal could succeed if planning obligations were in place to address specific concerns.

In appeal proceedings, getting the LPA to negotiate and sign a bilateral S106 within the inspector's timetable can be impractical — the council has lost the application and may have limited appetite to engage on the obligation package. A unilateral undertaking lets the developer offer the obligations as a deed, without needing the council to sign.

The inspector can then take the obligations into account when determining the appeal, provided the obligations meet the statutory tests (see below).

Negotiation Breakdown

On schemes where the developer and LPA have reached deadlock on the obligation package — for instance, where the council insists on contributions the developer considers unjustifiable — the developer can offer their proposed package as a unilateral undertaking. This puts the offer on the table as a binding commitment without requiring the council to agree to specific terms.

If the LPA then refuses permission, the unilateral undertaking forms part of the appeal evidence: "we offered these obligations, the council still refused."

Simplifying Obligations on Smaller Schemes

For smaller applications where the obligation package is straightforward — a single contribution to highways, for example — a unilateral undertaking can be quicker than negotiating a full bilateral S106. The developer drafts the undertaking, the LPA reviews it for content and enforceability, and it's executed without going through a multi-party legal drafting cycle.

What Unilateral Undertakings Can Do

A unilateral undertaking can include any obligation that's permissible under Section 106(1) — financial contributions, restrictions on the use of land, requirements to carry out works, requirements to provide infrastructure, dedications to public use. The substance of what it can deliver is the same as a bilateral agreement.

In practice, unilateral undertakings are most often used for:

Financial contributions — capital sums payable to the LPA on a defined trigger (typically commencement or occupation)
Affordable housing delivery — units to be transferred to a registered provider on defined triggers
Highway works contributions — payments to the local highway authority
Restrictions on occupation — for example, no occupation until the affordable units are completed
Travel plan commitments — measures to manage transport impact

What They Can't Do — Limits and Tests

The Statutory Tests

Whether bilateral or unilateral, any planning obligation has to meet the three tests set out in Regulation 122 of the Community Infrastructure Levy Regulations 2010. An obligation can only be a reason for granting (or in the case of an undertaking, supporting) planning permission if it is:

Necessary to make the development acceptable in planning terms
Directly related to the development
Fairly and reasonably related in scale and kind to the development

These tests apply to every obligation in a unilateral undertaking. An inspector or LPA officer reviewing the undertaking will measure each obligation against the tests; obligations that fail are typically given no weight in the planning decision.

Obligations That Need the LPA's Active Participation

Some obligations require the LPA to do something — manage a contribution, monitor delivery, hold funds in escrow. A unilateral undertaking can require the developer to pay a sum to the LPA on a trigger, but it can't bind the LPA to specific actions because the council isn't a signatory.

In practice this isn't usually a problem — the council still has its statutory monitoring duties under the IFS framework regardless of whether the obligation was bilateral or unilateral. But where the obligation specifically requires LPA cooperation (e.g. a deposit/refund mechanism, a complex review process), a unilateral undertaking is the wrong tool. A bilateral S106 is needed.

Multi-Party Obligations

Where the obligation involves a third party — a registered provider for affordable housing transfer, a highway authority for highway works — a unilateral undertaking from the developer alone may not bind that third party. Bilateral agreements that include all bound parties are the safer route on multi-party schemes.

How They Work in Practice

Drafting

The developer's solicitors draft the undertaking as a deed. It identifies the development (by reference to the planning application number), the site (by reference to title), and the specific obligations. Each obligation specifies the trigger, the amount or works, and any conditions.

Drafting needs to be done with the LPA's monitoring system in mind. An undertaking with vague triggers ("on completion of the development") or unspecified amounts ("a fair contribution to highway works") is unlikely to be considered enforceable, and won't be given weight in the planning decision.

Execution

The undertaking is executed as a deed by the developer (and any other party bound by it — for example, the landowner if different from the developer). The LPA doesn't sign. The document is then submitted to the LPA or the inspector as evidence of the obligations the developer has entered into.

Registration

The undertaking is registered against the title at the Land Registry. This is what makes it run with the land — binding successors in title to the same obligations.

Enforcement

Once registered, the LPA can enforce the undertaking the same way it would enforce a bilateral S106. Section 106 of the TCPA gives the council the power to seek injunctive relief and recover costs from any person bound by the obligation who is in breach.

What This Means for Councils

From the LPA monitoring perspective, a unilateral undertaking creates the same monitoring duties as a bilateral S106:

Financial obligations need to be invoiced and receipted
Spend-by deadlines need to be tracked
In-kind delivery needs to be verified
The annual Infrastructure Funding Statement needs to capture the obligations

There's no monitoring discount because the council didn't sign. The obligation is binding either way.

Councils sometimes object to unilateral undertakings on the basis that they lock the developer's preferred package in place without negotiation. The substantive answer is that the inspector or the council still has to apply the Reg 122 tests — obligations that fail those tests don't count. Procedurally, the council retains its monitoring and enforcement role unchanged.

Practical Considerations for Developers

Time the Drafting Right

A unilateral undertaking submitted late in an appeal — or worse, after the inquiry has closed — risks being given no weight. Draft early enough that it can be considered by the inspector during the substantive case.

Address the Reg 122 Tests Head-On

The most effective unilateral undertakings explicitly address why each obligation meets the necessary / directly related / fairly and reasonably related tests. An undertaking that just lists obligations without justifying them on the statutory tests is weaker evidence at appeal.

Don't Use Them to Pre-Empt Negotiation

Submitting a unilateral undertaking at application stage in lieu of engaging with the LPA's officer process is usually counterproductive. Officers tend to recommend refusal of applications where the developer has bypassed negotiation, and the appeal then has to argue the council was unreasonable to do so.

Plan for Title Registration

A unilateral undertaking that isn't registered against the title is unenforceable against successors. Title registration is part of the execution process, not an afterthought.

Summary

A unilateral undertaking is the developer's tool for entering binding planning obligations without the council's signature. It's most useful at appeal, on smaller schemes, or where negotiation has broken down. The statutory tests (Reg 122) apply just the same as for bilateral S106 agreements, and the LPA's monitoring and enforcement duties are unchanged.

For developers and planning consultants, the unilateral route is faster and less subject to council bargaining — but it requires careful drafting against the statutory tests, registration against the title, and the discipline to use it only where the bilateral route is unavailable or impractical.

Sources

Town and Country Planning Act 1990, Section 106 (subsection (1) — "by agreement or otherwise" enables unilateral form; subsection (9) — formal requirements)
Community Infrastructure Levy Regulations 2010, Regulation 122
GOV.UK Planning Practice Guidance — Planning Obligations