GDV Calculator Changelog

When source data refreshes or features ship, the entry lands here first. BCIS quarterly cuts, NPPF revisions, PPG-Viability updates, SDLT / LBTT / LTT rate changes all show up here. Audit trail for the data integrity stamp on every page.

2026-07-25 - Correctness re-verification

  • Bank Rate corrected to 3.75 percent (BoE held 18 Jun 2026); previously 4.00.
  • NPPF vintage corrected to Dec 2024 (amended Feb 2025) as the in-force framework; the Dec 2025 revision is a draft (consultation closed 10 Mar 2026), final expected Summer 2026.
  • PPG-Viability developer return restated as the 15 to 20 percent GDV range (17.5 percent midpoint), matching the guidance wording.
  • BNG statutory credit prices restated as £42,000 (tier A1, cheapest) to £650,000 (tier A5); the new 0.2ha small-site exemption and removal of the self-build exemption from 6 Aug 2026 added.

2026-06-24 - Launch (workbench v1)

  • Initial workbench shipped with 12 BCIS regions and 6 London borough deep-dives.
  • BCIS Q2-2026 build-cost bands wired in.
  • NPPF Dec 2024 + PPG-Viability Dec 2024 viability framing applied across the cost-line pages.
  • 9 scheme-type presets loaded.
  • 5-by-5 sensitivity heatmap on the hero.

2026-06-15 - BCIS Q2-2026 ingest

  • BCIS Q2-2026 vintage cut against Q1-2026 baseline.
  • Regional adjustment factors refreshed; NW remains baseline (index 100).
  • Conversion rate band tightened on the back of recent BCIS reporting.

2025-12-19 - Draft revised NPPF published (monitoring)

  • Draft revised NPPF published 16 Dec 2025 for consultation (closed 10 Mar 2026); final expected Summer 2026. In-force framework remains NPPF Dec 2024 (amended Feb 2025).
  • PPG-Viability 15 to 20 percent PoGDV range (17.5 percent midpoint) applied across viability and developer-return pages.
BCIS General Building Cost Index Q2 2026· Q2 2026Appraisal model reviewed by Oliver Wakefield-Smith (data integrity) with chartered-surveyor (MRICS) and CTA tax review. No affiliate links.