The new 20% housing land supply buffer: what it means from July 2026

The new 20% housing land supply buffer: what it means from July 2026

A significant change to the National Planning Policy Framework takes effect on 1 July 2026, and it could shift the planning position of dozens of local authorities across England overnight. Where a council's housing requirement was set under an older version of the NPPF and falls short of current housing need, it will now need to add a 20 per cent buffer to its five-year housing land supply.

For landowners and developers with sites ready to bring forward, this change is one of the more consequential planning updates of the year.

What is the 20% housing land supply buffer?

Every local planning authority is expected to demonstrate a five-year supply of deliverable housing sites, measured against its adopted housing requirement. A buffer is then added on top of that requirement, to allow for choice and competition in the land market and to account for any past under-delivery.

Historically, most authorities have applied a 5 per cent buffer, rising to 20 per cent only where the housing delivery test has shown significant under delivery. From 1 July 2026, a further route into that 20 per cent buffer opens up, based purely on how old and how ambitious an authority's adopted housing requirement is.

Under paragraph 78 of the NPPF, the new 20 per cent buffer applies for decision-making purposes where all the following are true:

• The authority's housing requirement was adopted within the last five years.
• That requirement was set under a previous version of the NPPF, rather than the version published in December 2024.
• The average annual housing requirement in the adopted plan is 80 per cent or less of the authority's current local housing need, calculated using the standard method.

Where all three conditions are met, the authority is effectively required to demonstrate six years of housing land supply rather than five, once the buffer is applied.

Why has the government introduced this NPPF change?

The measure is a deliberate piece of housekeeping. Many local plans adopted in recent years were built around housing requirements that are now lower than what the government's updated standard method suggests they should be.

Rather than forcing every one of those authorities to abandon its plan immediately, the NPPF gives them a transition period. But the trade-off for that breathing space is a tougher land supply test from July 2026 onwards. Authorities that update their plans and housing requirements in the meantime can avoid the buffer altogether, which is precisely the outcome the government is aiming for.

It sits alongside the government's wider push for 1.5 million new homes and a renewed emphasis on councils keeping their local plans current, rather than relying on numbers that were agreed several years ago and have since been overtaken by need.

How does tilted balance planning come into play?

This is where the change has real consequences for decision-making. If an authority cannot demonstrate a five-year supply, including the appropriate buffer, then the presumption in favour of sustainable development applies. This is commonly known as tilted balance planning.

In practice, the tilted balance means that planning permission should be granted unless the harm from a proposed development significantly and demonstrably outweighs its benefits, or unless specific protections apply, such as those covering Green Belt land or heritage assets.

Adding a 20 per cent buffer to an authority's requirement makes it considerably harder for that authority to hold a five-year supply, which in turn makes it more likely that the tilted balance will apply to housing applications in its area.

For an authority already close to the margin, this single change can be the difference between a defensible land supply position and one that falls short, opening the door to appeals and speculative applications that would previously have been resisted.

What role does the housing delivery test play?

The housing delivery test measures how many homes an authority has actually delivered against its requirement over the previous three years. It runs alongside, rather than instead of, the new July 2026 buffer rule.

An authority that scores below 75 per cent on the housing delivery test is already subject to the presumption in favour of sustainable development. One that scores below 85 per cent must already apply a 20 per cent buffer for that reason alone. The July 2026 change adds a separate, independent test based on the age and ambition of the adopted requirement, so an authority could now find itself subject to the 20 per cent buffer even if its recent delivery record looks reasonably strong.

Taken together, these tests mean that an authority's land supply position needs checking against several different criteria, not just one headline number.

What does this mean for landowners and developers?

For those promoting sites through land, planning and development, this NPPF change creates a genuine window of opportunity in the affected areas. Sites that were previously constrained by a defensible five-year supply position may become more deliverable once the buffer pushes that authority below the threshold.

Practical implications are likely to include:

• Stronger prospects on appeal for well-prepared housing applications in authorities that fall below the buffered supply figure.
• Increased scrutiny of housing land supply statements from July 2026 onward, as authorities recalculate their position against the new test.
• Renewed pressure on some authorities to accelerate local plan reviews, in order to avoid the buffer applying to their area at all.
• A need for up-to-date evidence on deliverable sites, since claims of a five-year supply will face closer challenge where the buffer applies.

None of this removes the need for a well-argued planning case. Tilted balance planning still requires the benefits of a scheme to be weighed properly against any harm, and protections for designated land and assets continue to apply regardless of an authority's supply position.

What should businesses and landowners do to prepare?

The starting point is to establish whether the local authority in question is likely to be caught by the new buffer. This means checking when its housing requirement was adopted, which version of the NPPF it was set under, and how that figure compares with the current local housing need under the standard method.

From there, it is worth reviewing any sites currently held or being considered against the likely change in planning position. A site that was marginal under the previous supply calculation may look considerably more attractive once the 20 per cent buffer is applied, particularly where planning applications and supporting evidence can be prepared in good time for July 2026.

Given how technical the interaction between the buffer, the housing delivery test, and tilted balance planning can be, specialist advice is strongly recommended before committing significant time or cost to a site.

Speak to our land planning and development team

Our land, planning and development specialists help landowners, developers, and businesses understand exactly how NPPF changes such as the new 20 per cent buffer affect the deliverability of their sites.

With more than 180 years of experience in the property sector, a proven track record of successful outcomes, and consistently positive reviews from clients, we build our advice around your site and your objectives, not generic assumptions about local policy.
Whether you are assessing a potential acquisition, preparing a planning application, or want to understand how a specific authority's housing land supply position is likely to change, call 0330 191 8107, email [email protected], or complete the contact form on our website to arrange a consultation.