Varying a section 106 agreement: the routes and the evidence

There are two ways to change a section 106 agreement, and the one most developers ask about is the one they should use last. By agreement with the local planning authority, an obligation can be modified or discharged at any time by deed, with no waiting period and no statutory test to satisfy. The statutory application route under section 106A(3) of the Town and Country Planning Act 1990 only opens once the relevant period has passed, which is five years from the date the obligation was entered into unless the deed says otherwise, and it comes with a test the authority applies rather than negotiates.

So the sequence is: negotiate first, apply second. And if the obligation was signed under five years ago, the application route is not open to you at all.

When an obligation can be renegotiated by agreement

Section 106A(1)(a) allows modification or discharge by agreement between the authority and the person against whom the obligation is enforceable. That is a deed of variation, and it is the workhorse.

Everyone with an interest in the land has to be party to it, which is where the timetable goes. A mortgagee will want its own advice. A registered provider that has contracted to take the affordable units has a commercial position. A management company that has taken on open space maintenance may need to consent. Identify the parties in week one, not week six.

Authorities will usually engage where the request is proportionate and the reason is intelligible. A change to a trigger point, a phasing amendment, a substitution of one highway work for another, a change in the tenure split at the request of the registered provider: these are ordinary business. A request to remove the affordable housing entirely is not, and it will be treated as a viability case whatever route you use.

The statutory route after five years

Section 106A(3) allows any person against whom the obligation is enforceable to apply to the authority for the obligation to be modified or discharged, once the relevant period has expired. Five years, unless the instrument specifies a different period.

The authority must determine the application on one of three bases:

1. That the obligation shall continue to have effect without modification.
2. That the obligation shall be discharged, if it no longer serves a useful purpose.
3. That the obligation shall continue to have effect subject to modifications, if it continues to serve a useful purpose but would serve that purpose equally well as modified.

Read limb 3 carefully, because it constrains what you can ask for. The modified obligation has to serve the original purpose equally well. You cannot use section 106A to bolt on a new obligation that was not in the deed, and you cannot use it to swap an affordable housing requirement for a smaller commuted sum unless you can show the modified version serves the purpose as effectively.

Procedure sits in the Town and Country Planning (Modification and Discharge of Planning Obligations) Regulations 1992, which set the form of the application and the notice requirements. The authority has eight weeks. Where it refuses, or fails to determine, section 106B provides an appeal to the Secretary of State, and the regulations set the deadline for bringing it. Check the current period before you rely on it.

One piece of history worth knowing. Sections 106BA to 106BC created a temporary route to review affordable housing obligations on viability grounds. Those provisions ceased to have effect on 30 April 2016, and any advice that refers to them is out of date.

Evidence for a variation on viability grounds

Where the case is that the scheme cannot carry the obligation, the evidence is an appraisal, and the authority will have it reviewed at your cost.

National viability guidance expects a residual land value approach benchmarked against existing use value plus a premium, with the inputs stated and justified. A Viability Assessment prepared for a variation faces a harder audience than one prepared at application stage, because the authority already accepted a scheme on the basis that the obligation was affordable.

Three arguments carry weight. Costs that have moved for reasons outside the applicant's control, evidenced by tendered figures rather than estimates. Values that have not materialised, evidenced by actual sales or by an agent's marketing record on the site itself. And a change in the affordable housing offer requested by the registered provider rather than by the developer.

One argument carries very little. That the land was bought at a price that assumed a lower obligation. Guidance is explicit that the price paid cannot justify a reduced contribution.

Publication is the other thing to plan for. Viability evidence submitted in support of an application is normally published, and an authority will resist redaction beyond material that is truly commercially sensitive.

Drafting a deed of variation

Keep it surgical. A variation that reopens the whole deed invites the authority's solicitor to update clauses you were content with.

The deed should recite the original agreement and its date, identify the clause being varied, set out the new wording, and confirm that the remainder of the agreement continues in full force. It should also deal with the land registry position, because the original agreement is usually protected by a restriction or notice on the title.

Costs are payable by the applicant, and the authority will ask for an undertaking before its legal team starts. Get the undertaking capped.

Appeals against refusal to modify

An appeal under section 106B is determined by the Planning Inspectorate on the same statutory tests, and the inspector is not conducting a fresh negotiation. The question is whether the obligation still serves a useful purpose and whether the modification you propose serves it equally well.

That framing rewards a narrow, well-evidenced ask. Appeals that amount to a request for a better commercial deal do not succeed.

Practical timing against the build programme

Programme the legal work alongside the planning work. Where a trigger requires an obligation to be met before occupation of a given plot, and the variation is not signed, the plot cannot be occupied. Lenders release funds against occupations.

Illustrative example: a 42-unit scheme where the registered provider changed its requirement from a mix of shared ownership and affordable rent to entirely affordable rent, needing a variation to the tenure schedule. Agreed by deed in about ten weeks, with the authority's costs capped at the outset. This example is illustrative.

Start the conversation with the section 106 officer before you instruct solicitors. Most variations that fail, fail because the ask arrived as a draft deed rather than as a question.

PlanScope drafts the Affordable Housing Statement and viability documents that support an obligation, structured to UK planning policy, with the appraisal inputs left for a qualified surveyor. Viability work is a field where councils expect a suitably qualified author, and professional review is strongly advised. Browse the full report list to see what a variation case usually needs, or enter a postcode on the PlanScope home page.

This is general guidance, not legal advice. Check the position with your local planning authority or a qualified professional before relying on it. PlanScope provides AI-assisted draft reports for planning applications. Reports should be reviewed before submission. We do not guarantee planning approval.