Phasing a scheme and when each threshold bites

Phased development thresholds work in two directions at once, and the distinction is worth getting right before the application is drafted. Policy thresholds are assessed on the whole permission: major development status, environmental impact screening, affordable housing percentages and transport assessment triggers all look at the scheme as a single project. Financial and delivery obligations can be broken down by phase: levy liability, biodiversity gain plans, occupation triggers and most condition discharges can all operate phase by phase, but only if the permission is drafted to allow it.

Get the second part wrong and you have a permission where nothing can start until site-wide information has been approved for land you do not intend to touch for six years.

What a phasing plan has to define

A phasing plan is a drawing plus a short document, and it needs to answer four questions.

Where each phase boundary runs, drawn to the same base as the red line and dimensioned. What is contained in each phase, in units, floorspace and infrastructure. What order the phases come in, and whether the order can change. And which parts of the site infrastructure, such as the spine road, drainage attenuation, open space and any off-site works, sit in which phase.

The last point is where most disputes arise. Attenuation basins, play space and estate roads serve more than one phase, and a plan that leaves them in a later phase creates a Grampian problem for the earlier ones. Allocate shared infrastructure to the phase that needs it first.

Where the phasing is secured by condition, the wording should allow the approved scheme of phasing to be varied with the authority's written agreement. Markets change over a ten-year build-out and an inflexible phasing condition is a section 73 application waiting to happen.

Thresholds assessed on the whole or the phase

The screening point is the one that carries legal risk. Assessment under the Town and Country Planning (Environmental Impact Assessment) Regulations 2017 applies to the project, and dividing a project into parcels each of which falls below a threshold does not avoid the obligation. Where a scheme will ultimately exceed a Schedule 2 threshold, screen the whole thing and say so. Where a full assessment follows, the Environmental Statement must be prepared by competent experts, and an Environmental Impact Assessment drafted in advance is a starting point for that team rather than a substitute for it.

Obligations tied to occupation triggers

Section 106 obligations on a phased scheme are usually expressed as occupation triggers rather than dates, because dates fail when a phase slips.

Typical drafting patterns:

1. No occupation of more than a stated number of dwellings in a phase until the affordable units in that phase are transferred.
2. No occupation of any dwelling in a phase until the estate road serving it is completed to base course.
3. No occupation of more than a stated total across the site until an off-site highway improvement is delivered.
4. Financial contributions payable on first occupation of each phase, indexed from the date of the agreement.
5. A review mechanism where a later phase has not started within a defined period.

Two drafting points repay attention. Define occupation, because beneficial occupation for a sales suite is not the same thing as residential occupation and developers and councils read it differently. And index every financial contribution, stating the index and the base date, because on a ten-year build-out an unindexed contribution is a windfall to one side.

Set the affordable housing position out clearly, phase by phase, in an Affordable Housing Statement, including the tenure split within each phase. Councils resist arrangements where the affordable element concentrates in the final phase, for obvious reasons.

Levy liability across phases

The Community Infrastructure Levy treats a phased permission differently from an ordinary one. Where the permission is subject to a condition requiring development to be carried out in phases, each phase is a separate chargeable development under the Regulations, which means liability is calculated, indexed and becomes payable for each phase independently.

That has three consequences worth planning for.

Indexation applies at the point each phase becomes liable, so later phases are charged at later index figures. On a long build-out that is a material cost and it should be in the appraisal.

Relief and exemptions are claimed per phase, on the prescribed forms, before work on that phase begins. Missing the sequence on phase three does not affect phases one and two, but the relief for phase three is lost.

The phasing condition has to exist for any of this to apply. A permission without one is a single chargeable development, and the whole liability crystallises when development first begins, which on a large site is a cash flow problem rather than a quibble.

Biodiversity gain plans by phase

For phased permissions the biodiversity gain regime works through two tiers: an overall plan covering the whole development, and a plan for each phase approved before that phase begins.

The overall plan establishes the site-wide baseline and how the 10 per cent gain will be achieved across the development, including any off-site units or statutory credits. Each phase plan then shows how that phase contributes, and it has to be consistent with the overall plan.

Two practical consequences. The baseline is fixed once, early, so get the habitat survey done before any enabling works, because degrading habitat after the relevant date does not reduce the baseline you are measured against. And on-site habitat creation frequently sits in a later phase while the losses occur in an earlier one, which creates a timing gap the authority will want secured by obligation and monitored for 30 years. A Biodiversity Net Gain Assessment should be completed by a competent person under the Environment Act 2021 regime, and a draft is a structured starting point for that person rather than a replacement.

Conditions that need phase specific discharge

This is where a well-negotiated permission earns its keep. A condition requiring details "before development begins" applies to the whole site unless it says otherwise, so a single site-wide drainage condition can hold up phase one while information is assembled for land nobody will touch for years.

Ask for conditions drafted in the form "before development begins within each phase" or "in respect of each phase". Conditions that really do need to be site-wide are a smaller set than authorities initially propose: usually the phasing scheme itself, strategic drainage design, the overall biodiversity gain plan, and archaeological evaluation where the strategy has to cover the whole site.

Review the draft conditions when they are sent for comment, not after the decision notice arrives. Changing a condition afterwards means a section 73 application, a fee and eight weeks. Our note on construction management requirements as site size increases covers the site-wide controls that do belong at whole-permission level, and statutory consultees that appear as a scheme grows sets out who will be commenting on them.

Drafting the phasing plan

A phasing submission that works looks like this. A phasing plan drawing with numbered phases, boundaries dimensioned and shared infrastructure allocated. A schedule per phase giving dwelling numbers, floorspace by use, affordable units and tenure, open space area and the infrastructure delivered. An indicative programme, clearly labelled indicative. A schedule of conditions showing which are site-wide and which are per phase. And a note on the levy and biodiversity position, confirming that each phase will be treated separately and referring to the phasing condition.

Then keep it consistent. The phase boundaries on the levy calculation, the biodiversity gain plan, the section 106 plan and the drainage strategy should be the same lines on the same drawing number. Where they diverge, someone will spend a month reconciling them, usually at the point a phase is ready to start.

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.