The DAT has been removed: what to do with your old appraisals

What happened

Homes England removed the Development Appraisal Tool (DAT) from GOV.UK on 20 April 2026, “because it relies on technology that is no longer supported”. The notice names no replacement. Appraisals built in the DAT will still come back at review.

Keep your old DAT appraisals usable

• Keep the original macro-enabled workbook untouched, and work on copies. Saving as .xlsx removes the macros.
• Print the full output, the summary, the quarterly cash flow and the input sheets to PDF.
• Record the DAT version, the Excel version, the appraisal date and the mode used.
• Copy the inputs into a plain CSV schedule. You will need it to rebuild the appraisal elsewhere.
• Keep re-saved versions together with the agreed one and its correspondence.
• Download the manual and training materials while they are still on GOV.UK.

What Residual does

Residual is browser-based viability software. It takes its three modes and its monthly cash flow from the DAT User Manual v4.1. It can't open DAT files, so you re-key the inputs.

Rebuilding the DAT's training exercise

Re-keyed in Residual, the DAT v4.02 self-training exercise gives a residual land value of £1,408,583 with the optional methodology settings on. The exercise publishes £1,417,383. The difference is £8,800 (0.62%).

Three conventions explain it, not different inputs. The DAT counts a year of rent as 52.18 weeks and a month as 30.5 days, and places fees once across the whole build. Residual uses 52 weeks, calendar months and fees for each phase. Neither is wrong. With the default settings, the difference is 0.98%.

Sources

All accessed on 23 October 2026. GOV.UK material is used under the Open Government Licence v3.0.

1. Homes England, Development appraisal tool, GOV.UK.
2. Homes England, DAT User Manual, version 4.1: PDF and accessible version.
3. Homes England, DAT v4.02 self-training exercise instructions.

Residual is independent and not endorsed by Homes England.