Phasing a large scheme without gaming thresholds

Phasing a large scheme is normal practice. Splitting one scheme into separate applications so that each falls below a threshold is not, and the regulations are written to catch it. The distinction that matters is whether the phases are parts of a single project being delivered over time, or a single project being presented as several smaller ones.

Get that wrong and the consequences arrive late: a screening direction pulling the whole site into Environmental Impact Assessment after two phases are consented, or an affordable housing requirement applied retrospectively across the landholding.

Legitimate phasing against artificial subdivision

Legitimate phasing usually looks like one permission, often outline with phases defined in a parameter plan, delivered in tranches against a programme. The evidence base covers the whole site. Obligations are apportioned. Infrastructure is tied to triggers.

Artificial subdivision looks different in ways an experienced officer spots quickly:

• Separate applications submitted within weeks of each other on contiguous land in the same ownership or control.
• Each application sitting a unit or two below a threshold, for instance nine dwellings twice rather than 18 once.
• Access arrangements that only make sense if the adjoining parcel is also developed.
• Drainage, open space or a spine road drawn to the red line edge and stopping there.
• The same design team, the same viability position and the same agent across both.

None of those is unlawful on its own. Together they invite the council to treat the parcels as one project, which is exactly the outcome the subdivision was meant to avoid.

There is a legitimate middle ground, and it is worth naming. Land does come forward in parcels for real reasons: ownership, ransom strips, phasing of a strategic allocation or funding. Where that is the position, say so in the planning statement and show the wider context plan. Concealment is what turns a defensible sequence into an indefensible one.

How cumulative effects are assessed

The Town and Country Planning (Environmental Impact Assessment) Regulations 2017 do not let a developer define the project narrowly and then screen it. Schedule 3 sets the selection criteria for screening Schedule 2 development, and cumulation with other existing or approved development is one of them. A nine-dwelling parcel next to a consented 40-dwelling parcel is screened against the combined effect on traffic, ecology, landscape and drainage.

The same logic runs through the rest of the evidence base. A Transport Assessment scoped for one phase and ignoring committed development on the adjoining parcel will be rejected by the highway authority, because the trip generation model has to include committed trips. Air quality, noise and surface water all work the same way.

Cumulative assessment also cuts in the developer's favour on occasion. Where a phase delivers infrastructure that reduces effects across the whole site, showing the cumulative picture is what justifies the mitigation package.

Screening and the whole project principle

Screening asks whether the development is likely to have significant effects on the environment. Courts have consistently treated the question as one about the project, not about the application, so the shape of the red line does not settle it.

Three practical consequences follow.

First, a screening opinion requested for one parcel should describe the wider proposals honestly. A screening opinion obtained on an incomplete description is vulnerable, and a competitor, an objector or a parish council can ask the Secretary of State for a screening direction under the 2017 Regulations.

Second, the local planning authority can screen of its own motion at any point before permission is granted. Discovering at committee that the scheme needs an Environmental Impact Assessment costs months, and where the assessment is required it must be prepared by competent experts under the 2017 Regulations, so a PlanScope draft is a starting point for that team rather than a substitute for it.

Third, retrospective repair is awkward. An Environmental Statement submitted after two phases are built has to assess a baseline that the development itself has already changed.

Section 106 triggers across phases

Obligations negotiated phase by phase tend to drift. The affordable housing percentage agreed on phase one becomes the anchor for phase two, and contributions calculated per dwelling produce a different total than a site-wide calculation.

A site-wide section 106 with phase triggers is usually the cleaner instrument. It can:

1. Fix the affordable housing tenure split and percentage across the whole site rather than per parcel.
2. Attach contributions to occupation triggers so they arrive with the demand they mitigate.
3. Include a review mechanism where delivery runs over several years.
4. Provide for stepping down obligations if a later phase does not come forward.

Where affordable housing is engaged, an Affordable Housing Statement covering the whole landholding is stronger than three separate ones, because it shows the council that the threshold is being met rather than avoided. The current National Planning Policy Framework, published on 17 August 2026, sets the national threshold above which affordable housing is sought; confirm the current wording and any local plan threshold before you model it, since both have moved in recent years.

Community Infrastructure Levy liability behaves differently again. The Community Infrastructure Levy Regulations 2010 allow each phase of a phased planning permission to be treated as a separate chargeable development, which affects when the levy becomes payable and how relief and exemptions are claimed. That is a reason to define phases properly in the permission rather than informally on a programme.

Infrastructure delivery and Grampian conditions

Grampian conditions prevent development, or occupation, until something happens off site or on land outside the applicant's control. They are the standard tool for tying a spine road, a signalised junction or a pumping station to a phase.

They also expose subdivision. A condition preventing occupation of phase two until an access built in phase one is complete is an admission that the two parcels are one project. Better to make that admission at the start, in a phasing plan submitted with the application, than to have it drawn out of you at committee.

Practical sequencing questions worth settling early: which phase carries the surface water attenuation for the whole catchment, which phase delivers the play space, and what happens to the biodiversity gain plan if the later phases stall. The biodiversity gain condition under the Environment Act 2021 regime has specific provision for phased development, requiring an overall plan alongside plans for each phase, and the 30-year management obligation does not reduce because a phase was delayed.

Risks of separate applications on one landholding

The exposure sits in four places.

Screening risk, already covered, is the largest. Validation risk comes next: a council that considers the application a fragment can refuse to validate it until the wider proposals are described, and local validation lists increasingly ask for a site context plan.

Then there is appeal risk. An inspector who concludes that the appeal scheme is part of a larger project can dismiss on the basis that the evidence before them does not assess the real effects. And there is reputational risk with the authority you will be dealing with for the next five years, which is harder to price and easy to underestimate.

Consultee thresholds move with scale too, and the pattern of statutory consultees that appear as a scheme grows is worth checking against the whole site rather than the parcel in front of you.

Presenting a phasing strategy honestly

The submission that works contains four things: a site context plan showing the whole landholding and its ownership, a phasing plan with indicative parcels and a delivery sequence, an evidence base scoped to the whole project, and a planning statement that explains why the phases are separated.

Say what you know and flag what you do not. A phasing plan marked indicative, with a mechanism in the section 106 for approving a revised sequence, is more credible than a precise programme nobody believes.

This is general guidance, not legal advice; check the position with your local planning authority or a qualified professional before relying on it.

Enter your postcode on PlanScope to see which reports the whole site is likely to need before you decide how to phase it. PlanScope provides AI-assisted draft reports for planning applications. Reports should be reviewed before submission. We do not guarantee planning approval.