What Happened to the Homes England Development Appraisal Tool in 2026?
Homes England removed its Development Appraisal Tool in April 2026. Here is what changed, what the old DAT was used for and how teams should replace the workflow safely.
4 min read
Homes England removed its Development Appraisal Tool on 20 April 2026 because the tool relied on technology that was no longer supported. The GOV.UK publication page and user-manual material remain useful background, but the downloadable tool itself was withdrawn. Homes England directs organisations significantly affected by the removal to its DAT enquiries contact.
For development teams that used DAT as a standard viability model, the practical question is not just which spreadsheet replaces it. It is how to preserve the assumptions, review method and audit trail that made the model useful in the first place.
How This Works
The old Development Appraisal Tool was a site-specific viability model used for purposes including scheme viability, planning obligations, affordable housing and potential land value.
Its removal does not remove the need for development appraisals.
Teams still need a controlled way to model:
scheme and tenure
development value
build and infrastructure costs
professional fees and contingency
planning obligations
programme and cash flow
finance
developer return
residual land value or surplus/deficit
sensitivity
There are now three broad routes a team can take.
Maintain A Controlled Internal Spreadsheet
A well-governed spreadsheet can still work.
The key is governance: version control, locked formulas where appropriate, documented assumptions, clear ownership and a review process.
The risk is not “Excel” by itself. The risk is an undocumented model copied from project to project until nobody is sure which formulas, assumptions or overrides are current.
Use Purpose-Built Development Appraisal Software
Purpose-built software can standardise calculations, scenarios, reporting and audit trails.
Before switching, check that the product matches the appraisal type your team actually runs. A model designed for a simple residential feasibility screen is not automatically suitable for every mixed-use, phased, affordable or finance-heavy scheme.
Use A Firm-Specific Appraisal Workflow
A third option is to keep the financial model inside the wider site workflow.
That means the appraisal is connected to the planning evidence, comparables, source documents, site record, decision history and later revisions instead of living as a detached file.
The benefit is not simply a different calculator. It is less re-keying and a clearer evidence trail from source to assumption to decision.
Worked Example
Suppose a land team previously used DAT for first-pass residential viability.
A new site arrives with an agent brochure, a boundary plan and an asking price.
The weak migration is to download a new spreadsheet and manually rebuild the old process field by field.
A stronger migration starts by defining the team’s standard appraisal dictionary:
Site and scheme
Values
Affordable housing
CIL and Section 106
Build and externals
Abnormals
Professional fees
Contingency
Programme
Finance
Target return
Residual land value
Sensitivity
Decision
Source and date for every material assumption
Once that structure is agreed, the tool can change without the appraisal discipline disappearing with it.
That is the part worth preserving.
Review Method
If your team is replacing DAT or another legacy appraisal model, review the replacement against six questions.
1. Can we see every material assumption?
2. Can we identify the source and date behind each important input?
3. Can we run and compare scenarios without losing the original?
4. Can we inspect the cash flow and finance rather than only the headline output?
5. Can we see sensitivities that could change the decision?
6. Can another person review the appraisal without asking the original modeller what the spreadsheet means?
If the answer to the sixth question is no, the replacement is still person-dependent.
Sources Used
Homes England, Development appraisal tool publication page:
https://www.gov.uk/government/publications/development-appraisal-tool
Homes England, Development appraisal tool user manual:
Homes England, Financial viability for housing-led projects:
https://www.gov.uk/guidance/financial-viability-for-housing-led-projects
GOV.UK, Planning Practice Guidance: Viability:
https://www.gov.uk/guidance/viability
RICS, Valuation of development property:
Limitations And Professional Review
Homes England’s removal of DAT does not amount to an endorsement of any specific replacement product.
This article is about workflow and model governance, not a recommendation that one tool is suitable for every appraisal purpose.
Planning viability, market valuation, lending, tax, cost planning and other professional uses can require their own standards, evidence and qualified review.
Any team migrating a legacy model should validate formulas, assumptions, outputs and reporting against its own requirements before relying on the replacement for live decisions.
Where Harold Viability Fits
Harold Viability is designed as a firm-specific site appraisal workflow rather than a generic replacement for one retired spreadsheet.
The current model can keep the site evidence, development schedule, value and cost assumptions, planning obligations, finance, residual land value, cash flow, sensitivity and decision record together.
That makes the model easier to inspect and update as new evidence arrives.
It does not remove the need for professional review. It reduces the amount of repeated assembly between receiving a site and getting to a decision-ready first appraisal.
Related reading:
What is a development viability appraisal?
For wider land-workflow context:
Article written by
