Unilateral undertaking: a section 106 the council does not sign

A unilateral undertaking is a planning obligation you give on your own, without the council signing anything. Section 106 of the Town and Country Planning Act 1990 allows a planning obligation to be entered into by agreement with the authority or by any person with an interest in the land acting alone, and the second route is the unilateral undertaking. It is a deed, it binds the land rather than you personally, and it is registered as a local land charge so every future buyer sees it.

For a self-builder the usual reason to reach for one is simple: you need an obligation in place, and waiting for the council's legal team to negotiate and seal a bilateral agreement would cost more time and money than the obligation itself is worth.

What it is and how it is made

The statute sets out what the deed has to contain. It must be executed as a deed, state that it is a planning obligation for the purposes of section 106, identify the land, identify the person entering into it and their interest in that land, and identify the local planning authority by whom it is enforceable.

Get any of those wrong and the document may not be a planning obligation at all, which is a discovery usually made at the worst possible moment.

The obligation itself can do four things: restrict the development or use of the land, require specified operations or activities to be carried out, require the land to be used in a specified way, or require a sum to be paid. Most small undertakings do the first or the last.

Crucially, the council is not a party. It gives nothing, promises nothing and signs nothing. That asymmetry is the source of both the advantage and the limitation.

When it is used instead of a bilateral agreement

Four situations come up repeatedly.

The council is slow or unwilling. On small applications an authority may have no capacity to negotiate a deed for a modest contribution, and a unilateral undertaking lets you deliver the obligation without their engagement.

The obligation is simple. A single payment, an occupancy restriction, or a tie preventing an annexe being sold separately from the main house needs no negotiation and no reciprocal promises.

You are at appeal. The authority may decline to negotiate an agreement for a scheme it has refused, so an undertaking is often the only route. More on that below.

The obligation is contested. Where you think the council is asking for something it is not entitled to, an undertaking lets you offer what you accept is justified while arguing that the rest fails the statutory tests.

Where the arrangement needs the council to do something, a unilateral undertaking will not work. Refund clauses if money is unspent after a period, review mechanisms requiring the authority to recalculate, or any obligation on the council to apply funds in a particular way all need a bilateral deed, because a party who has not signed cannot covenant.

Who must be a party, and why title matters

The obligation binds the interest of the person who gives it, and anyone deriving title from them. That sentence does a lot of work.

If the freeholder gives the undertaking, it binds the freehold. If only a leaseholder gives it, the freeholder is not bound and neither is anyone taking a new lease from the freeholder. So the first step is always a title check: obtain the office copy entries, identify every interest capable of frustrating the obligation, and bring them all in.

Mortgagees matter most. A lender with a charge over the land is not bound by an obligation given after the charge unless it joins in or consents, and a lender exercising its power of sale could in principle pass the land free of it. Councils know this, and most will refuse to treat an undertaking as adequate unless the mortgagee has consented. Ask your lender early, because consent can take several weeks and lenders charge for it.

Options, restrictive covenants, rights of way and unregistered strips all need checking too. A ransom strip in third party ownership across the access is not bound by anything you sign. Once completed, the obligation appears on searches in the way described in local land charges and how obligations appear on title.

Using one at appeal

Appeals are where unilateral undertakings are most common, and where the drafting needs most care.

The Planning Inspectorate expects a completed obligation, properly executed, before the inquiry or hearing closes or by a stated deadline in written representations. A draft is not enough. An engrossed and dated deed is.

Three points of practice make the difference.

First, the inspector will test the obligation against the statutory tests: whether it is necessary to make the development acceptable in planning terms, directly related to the development, and fairly and reasonably related in scale and kind. An obligation failing those tests cannot be taken into account, so explain in your statement of case why each limb is met rather than leaving the inspector to infer it.

Second, you can offer alternatives. A well drafted undertaking can contain obligations that take effect only if the inspector reaches a particular conclusion, which lets you cover the council's case without conceding it. Draft the trigger clearly.

Third, make it conditional on the appeal being allowed and the permission being implemented. An undertaking that bites on signature rather than on implementation leaves a burden on the land after a dismissed appeal.

Send the draft to the council in good time even though they are not signing it. Their comments on drafting are usually sensible, and an inspector will note whether the parties discussed it.

Drafting so the obligation is enforceable

The council will enforce this document, possibly years from now, possibly against someone else. Write it accordingly.

1. Define the development precisely by reference to the application number and the drawings, and say what happens if that permission is varied under section 73 or amended under the route described in section 96A non-material amendments.
2. Express every obligation as a covenant with the local planning authority, not as a statement of intent.
3. Make triggers objective and datable: the start of development on site, occupation of the first dwelling, a fixed number of days after a defined event. Avoid "as soon as reasonably practicable".
4. Set out payment mechanics in full, including the account, the notice to be given, indexation if any, and interest on late payment.
5. Include a notice clause and a provision requiring a purchaser to be told about the obligation.
6. State that the obligation ceases to bind anyone who has parted with their interest, which is standard and protects you after you sell.

Avoid indexing to a measure nobody can find in fifteen years, and avoid obligations expressed as percentages of figures that will not exist by the time they bite.

Registration, discharge and later modification

Once completed, the undertaking is registered as a local land charge by the authority, which is how a buyer's solicitor finds it. It runs with the land indefinitely unless it says otherwise, so consider whether it should fall away on a stated event, such as the permission expiring unimplemented.

Modification and discharge are governed by section 106A. The obligation can be discharged or modified at any time by agreement with the authority, which is the usual route and needs a further deed. Failing agreement, an application can be made to the authority after the relevant period has passed, which is five years from the date the obligation was entered into, with a right of appeal to the Secretary of State if the authority refuses or fails to determine it.

The test on such an application is whether the obligation still serves a useful purpose, or whether it would continue to serve that purpose equally well if modified. It is not an opportunity to reopen a bargain you regret.

One last point for self-builders. A unilateral undertaking is a deed affecting your land for the foreseeable future, and the cost of a solicitor drafting it properly is small against the cost of getting it wrong. Where the obligation is more than a single payment, take advice. Related timing questions on outline schemes are covered in reserved matters: scope, timing and common refusals.

PlanScope drafts Planning Statements and the supporting documents that sit alongside an obligation, structured to UK planning policy and flagged where site facts are missing. Browse the report types to see what your application is likely to need. Reports are AI-assisted drafts that should be reviewed before submission, and we do not guarantee planning approval. This is general guidance, not legal advice: a planning obligation is a legal deed and should be prepared or checked by a solicitor.