Deliverable site: the housing land supply definition
Deliverable means available now, suitable now and achievable with a realistic prospect of delivery in five years. The glossary splits sites into two groups with very different evidential burdens.
A deliverable site, in the National Planning Policy Framework glossary, is one that is available now, offers a suitable location for development now, and is achievable with a realistic prospect that housing will be delivered within five years. Everything in a five year housing land supply dispute turns on that deliverable site definition, because the authority and the appellant are usually arguing about the same sites and disagreeing about whether the evidence meets the test.
The glossary then splits sites into two groups with different evidential burdens, and that split is where most of the argument happens. Read the current edition, published on 17 August 2026, rather than a version carried forward in an old appeal statement, because the Framework has been reissued twice since 2023.
Available, suitable, achievable
Three words, each doing separate work.
Available means the site can be developed now. Ownership is not fragmented in a way that blocks delivery, there is no ransom strip, no sitting tenant with security of tenure, no restrictive covenant that has not been dealt with.
Suitable means it is an appropriate location for housing now, taking policy and constraints as they stand. A site needing a plan allocation that has not happened yet is not suitable now.
Achievable means there is a realistic prospect of completions within five years. This is the test that carries most of the weight and the least precision, and the Court of Appeal in St Modwen Developments Ltd v Secretary of State for Communities and Local Government in 2017 confirmed that it asks for a realistic prospect rather than certainty.
That last point is worth holding onto. Objectors sometimes argue a site is not deliverable because delivery is not certain, which misstates the test. Authorities sometimes argue the reverse, that a realistic prospect means almost any permission counts. Both are wrong.
The two categories and their different tests
The glossary treats one group as deliverable unless there is clear evidence to the contrary, and the other as deliverable only where there is clear evidence that completions will begin within five years. The burden flips between them.
| Site type | Starting position | Who has to produce evidence |
|---|---|---|
| Detailed permission for housing | Deliverable until permission expires | Objector, with clear evidence of non-delivery |
| Non-major site with permission | Deliverable until permission expires | Objector, with clear evidence of non-delivery |
| Outline permission for major development | Not assumed deliverable | Authority, with clear evidence completions will begin |
| Allocated in a development plan | Not assumed deliverable | Authority, with clear evidence completions will begin |
| Permission in principle | Not assumed deliverable | Authority, with clear evidence completions will begin |
| On a brownfield register | Not assumed deliverable | Authority, with clear evidence completions will begin |
The examples the glossary gives of clear evidence that homes will not be delivered are instructive: the site is no longer viable, there is no longer demand for the type of units, or the site has long term phasing plans. Those are the arguments that work against a permitted site, and the common thread is that each needs evidence rather than assertion.
For the second category the question is narrower than people assume. It is not whether the site will complete within five years. It is whether completions will begin within five years. A large allocation with a realistic prospect of first completions in year four counts, even though most of its units land outside the period.
Clear evidence, in practice
Clear evidence for a site in the second category is almost always a combination of these.
A written statement from the landowner or developer confirming the intention to develop, the current programme and the anticipated date of first completions.
Evidence of a planning route that works: a reserved matters application submitted or in preparation, pre-application engagement under way, conditions capable of discharge.
Evidence that the infrastructure constraint has a solution: a signed section 278 agreement, a utility connection offer, a confirmed route for foul drainage, a water undertaker position.
Evidence of a developer with capacity on site, which is the strongest single item and the one authorities find hardest to produce for sites still in promoter hands.
A statement from a site promoter with no contracted housebuilder is weaker than it looks. Inspectors have repeatedly treated promoter aspiration as insufficient on its own, and those decisions are indicative of how the test is being applied rather than binding precedent.
Lead-in times and build-out rates
The arithmetic is where supply arguments are won. Two variables set the output: how long it takes from the base date to the first completion, and how many units a year the site then delivers.
Lead-in time for a major site covers reserved matters or full application determination, condition discharge, section 106 completion, site preparation, infrastructure and the construction period to first occupation. On a large site each of those stages is measurable and each should be evidenced rather than assumed. Authorities that apply an average lead-in across all sites are inviting a challenge on the sites that plainly do not fit the average.
Build-out rate depends on outlet numbers. A single housebuilder on one sales outlet delivers at a very different rate from three builders on three parcels, and the local evidence base should say which is assumed. Where it does not, ask.
Both figures should come from local completion records rather than national averages, and both should be tested site by site for the largest contributors to the supply. On most authorities a handful of sites make up a large share of the five year figure, so the dispute is usually about three or four sites rather than about fifty.
Testing a published trajectory
Work through it in order rather than attacking the total.
- Confirm the base date and check that completions and permissions are counted to the same date, since mismatched dates inflate supply.
- Separate the two glossary categories and check that sites in the second category each have evidence attached rather than a row in a table.
- For each of the largest sites, test the lead-in assumption against the actual planning position on the authority's own register.
- Test build-out against the number of outlets realistically achievable.
- Check for double counting between an allocation and a permission on the same land.
- Check whether any site appears with completions in year one where no application has yet been determined.
Step six finds errors more often than it should, and any applicant can ask that question without a consultant.
The output of that exercise belongs in the planning statement rather than in a separate document, with the supply calculation set out as a table so the officer and any inspector can follow the working. Where the argument is that a site in the authority's supply is not viable, a viability assessment prepared to the RICS approach is the supporting evidence, and councils expect a suitably qualified author for that work.
Housing land supply is one of those topics where the policy text is short, the glossary does the heavy lifting, and the outcome depends on evidence about specific sites. If you are relying on a shortfall, build the case site by site. A general assertion that the trajectory is optimistic persuades nobody.
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. Browse the 66 report types by category to scope the evidence base for a major residential application.
Frequently asked questions
Does a site have to complete within five years to be deliverable?
No. For sites with outline permission, allocations, permission in principle or brownfield register entries, the test is whether completions will begin within five years. A large site whose first completions land in year four counts, and only the units expected inside the period are included in the supply figure.
Who has to prove deliverability?
It depends on the category. Sites with detailed permission and non-major sites with permission are treated as deliverable until the permission expires unless there is clear evidence homes will not be delivered. For the other categories the authority has to produce clear evidence that completions will begin within five years.
What counts as clear evidence that completions will begin?
Typically a written statement from the landowner or developer with a dated programme, evidence of a planning route under way such as a submitted reserved matters application, evidence that infrastructure constraints have a solution, and evidence of a housebuilder with capacity. Promoter aspiration without a contracted builder is treated as weak.
Is a site with an expired permission still deliverable?
The glossary treats permitted sites as deliverable until the permission expires, so an expired permission removes that starting assumption. The land may still be deliverable if it is allocated or carries another status, but it then falls into the category needing clear evidence that completions will begin within five years.
Where do lead-in and build-out assumptions come from?
They should come from local completion records and from the planning position of each site, not from national averages applied uniformly. Lead-in covers determination, condition discharge, obligation completion, site preparation and construction to first occupation. Build-out depends on the number of sales outlets realistically achievable on the site.
Sources and further reading
This article is general guidance about the planning system in England and, where stated, the rest of the UK. It is not legal or professional advice. Check your local planning authority’s validation requirements and take professional advice for your specific site.