Unilateral Undertaking

 

A unilateral undertaking is a planning obligation you give on your own. It is made under the same section 106 of the Town and Country Planning Act 1990 as a Section 106 Agreement, it binds the land in the same way, and it is enforceable by the council in the same way. The difference is that the council does not sign it.

That single difference is what makes it useful. It is also what makes it dangerous, and both halves of that are worth understanding before you offer one.

 

 

What a unilateral undertaking is

 

Section 106(1) allows any person interested in land to enter into a planning obligation “by agreement or otherwise”. Those last two words are the whole of it. A unilateral undertaking is the “otherwise”: a deed given by the landowner to the council, containing obligations the council can enforce, without the council being a party to the document.

Everything else about it is a section 106. It binds successors in title. It is a local land charge. It has to be executed as a deed and satisfy the same formalities. It has to pass the same three tests under regulation 122 of the Community Infrastructure Levy Regulations 2010: necessary, directly related, fairly and reasonably related in scale and kind.

One thing it cannot do: it cannot bind the council. The council is not a party, so nothing in it obliges the authority to do anything. Obligations flow one way only.

 

Why anyone would use one

 

Speed, and the fact that a negotiation needs a willing counterparty.

A bilateral Section 106 Agreement takes months, largely because it takes two organisations to draft, review and execute it. A unilateral undertaking takes weeks, because it takes one. When the obstacle is not the substance of the obligation but the council’s capacity to get to it, a unilateral undertaking removes the bottleneck.

The classic use is at appeal. Your application was refused for want of an obligation. You cannot make the council negotiate one now, and even if it would, the timetable will not wait. So you offer the obligation unilaterally and put it in front of the inspector. It may or may not have been negotiated with the council in advance.

The other use is proactive: offering an undertaking alongside an application to strengthen your position, heading off an objection before it becomes a reason for refusal.

 

Unilateral undertakings at appeal: the timing rules

 

This is where undertakings most often go wrong, and it is not usually the drafting.

The Planning Inspectorate’s procedural guidance is explicit: obligations received after the deadlines are taken into account only at the inspector’s discretion. The deadlines depend on the route:

• Written representations: submit an executed and certified copy of the obligation when you make the appeal
• Hearing or inquiry: a final draft agreed by all parties should reach the Inspectorate no later than ten working days before it opens

“At the inspector’s discretion” is not a safety net. It means exactly what it says, and inspectors have refused to exercise it.

It is also your job, from the outset, to establish what the relevant legal interests in the land are and who holds them. The council has a duty to check what you provide and advise the inspector whether the ownership position is agreed. Get the interests wrong and the undertaking may not do what you think it does. That is why a mortgagee’s consent matters, and why it is often the thing that delays execution.

 

Tiwana: an inspector cannot simply ignore one

 

The most important recent case, and a useful one to know about.

In Tiwana Construction Ltd v Secretary of State for Housing, Communities and Local Government [2025] EWHC 1485 (Admin), decided by Eyre J on 24 June 2025, an appeal concerned ten self-build houses at Burwell in West Suffolk. The council had refused permission partly for lack of affordable housing. At the hearing the appellant offered to commit three of the dwellings as affordable, and the inspector set a deadline for a completed Section 106 agreement, then extended it.

The appellant’s mortgagee could not sign in time. So rather than miss the deadline entirely, the appellant submitted a completed unilateral undertaking instead, with a solicitor’s note explaining why it should be accepted and that an agreement would take longer.

The inspector disregarded it and dismissed the appeal. The High Court quashed the decision, holding that in disregarding the undertaking the inspector irrationally failed to have regard to an obviously material consideration.

Two practical points come out of it. A unilateral undertaking is not a second-class document: it is a planning obligation, and if it is before the inspector it is a material consideration that has to be dealt with. And the mortgagee problem is real and common: it is frequently the lender’s signature, not the developer’s, that cannot be obtained to a deadline. If your land is charged, start that conversation early.

Do not over-read it. The court’s finding was that the inspector could not simply ignore the undertaking, not that it had to be given weight, still less that the appeal had to succeed. The threshold for quashing on irrationality is a high one, and this cleared it because the inspector had made a conscious decision to side-step the issue.

 

Millgate: why you cannot take it back

 

The case that cuts the other way, and the reason to think hard before you execute.

In R (Millgate Developments Ltd) v Wokingham BC [2011] EWHC 6 (Admin), the developer delivered an executed unilateral undertaking to the inspector during an appeal, promising financial contributions towards local facilities, in order to meet the council’s objection. It made no submissions arguing the contributions were unnecessary. The appeal succeeded.

The developer then argued it should not have to pay, on the basis that the obligations had not been shown to be necessary. It lost. The deputy judge noted there was no condition in the undertaking that the obligation should take effect only if an inspector indicated it was necessary to make the development acceptable. The undertaking had been entered into willingly. Its enforceability was a separate question from whether the contributions were justified.

The lesson is blunt: a unilateral undertaking you offer to win an appeal is a unilateral undertaking you have given. Winning does not release you from it, and neither does later deciding the money was never really needed. Government guidance puts the same point plainly: take great care before executing, because once an obligation has been entered into and executed it will not usually be possible to withdraw or modify it unilaterally.

One route Millgate points at: an undertaking can be drafted so an obligation only bites if the inspector indicates it is necessary. If you are offering contributions you are not convinced you owe, that conditionality is worth asking your solicitor about.

 

Getting out of one

 

The same routes as any section 106, and they are not generous.

You can agree a variation with the council at any time under section 106A(1)(a), but the council has to be willing, and it is under no obligation to be. Otherwise you are waiting five years from the date the obligation was entered into before you can apply to modify or discharge it under section 106A(3). If that application is refused, there is a right of appeal to the Secretary of State under section 106B, within six months.

The full detail is on our Section 106 Agreement page. The short version: an undertaking is quick to give and slow to undo, and the asymmetry is the point.

 

Should you offer one?

 

Sometimes, and with advice.

The case for is genuine. If the council will not or cannot negotiate in your timescale, a unilateral undertaking is the only way to put an obligation in front of a decision-maker. At appeal it is often the difference between an inspector who can grant permission and one who cannot.

The case for caution is Millgate. You are drafting an enforceable obligation, alone, against a deadline, and you will live with it for at least five years. Offering more than is necessary to be safe is a real temptation and a real mistake: every pound you volunteer is a pound you have promised.

Three things worth doing:

• Get it drafted by someone who does section 106 work. It is a deed of obligation, not a letter of intent, and general conveyancing experience is not the same thing
• Ask about conditionality: whether the obligation can be tied to the inspector finding it necessary
• Sort the land interests and the mortgagee first. Tiwana turned on a lender who could not sign in time, and that is the commonest cause of a missed deadline

If you are heading to appeal, see our guide to how to appeal against a decision. For the obligation itself and the tests it must pass, start with Section 106.

Unilateral Undertaking relevant legislation

Read the “Changes to Legislation” panel at the top of each page before relying on the text.

• Section 106, Town and Country Planning Act 1990: “by agreement or otherwise”
• Section 106A, Town and Country Planning Act 1990: modification and discharge
• Section 106B, Town and Country Planning Act 1990: appeals
• Regulation 122, Community Infrastructure Levy Regulations 2010: the three tests
• Tiwana Construction Ltd v SSHCLG [2025] EWHC 1485 (Admin)

Developer contributions & planning agreements

 

 

Unilateral Undertaking Page Updated: 25th August 2026