A viability negotiation can lose momentum long before anyone agrees the figures. Different assumptions, unexplained cost allowances and inconsistent versions of an appraisal can leave developers and council reviewers discussing different schemes.
A shared methodology gives that conversation a firmer starting point. For developers seeking to demonstrate what a scheme can reasonably contribute, the strongest case combines current planning policy, the relevant RICS standards and evidence that another professional can interrogate.
Start with the current policy position
The National Planning Policy Framework published in August 2026 now addresses development viability through policy DM5. It identifies circumstances that may justify an assessment, including material differences in development type or site characteristics, previously unaccounted-for costs and significant changes in site or economic circumstances. Assessments must explain departures from the evidence underpinning the development plan. Neither the purchase price nor an intended option price justifies non-compliance. Read NPPF policy DM5.
This makes the opening question practical: what is different about this proposal, and where is the evidence? A short explanation supported by the relevant surveys, cost information and market analysis is a more useful starting point than simply presenting a disappointing residual value.
Use RICS standards to structure the assessment
RICS’ Assessing viability in planning under the National Planning Policy Framework 2019 for England was published in 2021 and reissued as a professional standard in April 2023. Its title retains the earlier policy date; practitioners must also consider the current national framework and applicable local policies. The standard sets out an approach aligned with government guidance, including benchmark land value and standardised inputs. Read the RICS assessment standard.
The companion Financial viability in planning: conduct and reporting standard establishes mandatory requirements for RICS practitioners, with objectivity and transparency central to the process. A well-presented appraisal should make its assumptions and reasoning accessible to the people who must review it. Read the RICS conduct and reporting standard.
Make the appraisal easy to follow
At its simplest, residual appraisal deducts development costs and an appropriate developer return from the development’s value, then compares the resulting land value with an independently justified benchmark. The calculation is only as persuasive as its inputs.
Government viability guidance uses existing use value plus a landowner premium as the starting point for benchmark land value. It also stresses evidence and transparent presentation. Its December 2025 update expressly allows a decision-maker to request an updated assessment where clear interpretation is not possible. Read the Planning Practice Guidance on viability.
In practical terms, every significant figure should have a clear route back to a source: an adjusted sales comparable, a cost plan, an infrastructure quotation or an explained professional assumption. State the valuation date, use consistent floor areas and show how the affordable housing mix affects receipts.
Turn disagreement into a manageable schedule
Our recommended negotiation workflow is straightforward:
- Establish the baseline. Fix the scheme description, accommodation schedule, policy requirements and appraisal date before comparing conclusions.
- Record the evidence. Give each material assumption a source, date and explanation, with outstanding information clearly identified.
- Isolate the differences. Put the applicant’s and reviewer’s positions side by side and calculate the effect of each disputed input.
- Test credible alternatives. Explore the impact of changes in values, costs, timing and tenure without quietly changing unrelated assumptions.
- Maintain one change record. Record what was agreed, what remains disputed and which version contains the current position.
For example, if the disagreement concerns drainage, the next step can be a focused reconciliation of scope, quantities and quotations. That is easier to resolve than a broad argument about whether the overall construction allowance feels too high.
A clearer route to agreement
Recognised methodology can reduce avoidable clarification and help both sides concentrate on the assumptions that affect deliverability. It cannot guarantee a reduction in contributions or a particular decision timetable.
Bartons supports developers with viability assessment, report preparation and negotiations with council-appointed reviewers. If affordable housing or S106 requirements are affecting your scheme, speak to Bartons about an evidence-led viability assessment.