Gera Council Tax Band Index — Methodology
A fully reproducible formula for the Gera Council Tax Band Index (GCTBI). Every computation uses only the real MHCLG Band D figure (OGL v3.0) and the fixed statutory ratios from the Local Government Finance Act 1992 — no estimates, no proprietary inputs.
The formula
GCTBI(area, band) =
(england_band_amount − area_band_amount)
─────────────────────────────────────── × 100
england_band_amount
where:
area_band_amount = area_bandD × band_ratio
england_band_amount = england_bandD × band_ratio
band_ratio = { A:6/9, B:7/9, C:8/9, D:1, E:11/9, F:13/9, G:15/9, H:18/9 }
(Local Government Finance Act 1992, s.5)
Positive GCTBI → area is cheaper than England average for that band.
Negative GCTBI → area is more expensive than England average for that band.
GCTBI for England aggregate → 0 (by definition).Step-by-step
- 1Download the MHCLG source data. The file
Band_D_2026-27.ods(Table 5) from the MHCLG "Council Tax levels set by local authorities in England 2026 to 2027" publication provides the total Band D area council tax for every billing authority, including all precepts. Licensed OGL v3.0. - 2Derive all 8 bands. Apply the statutory ratios from the Local Government Finance Act 1992 s.5. These ratios are fixed in law and are identical for every billing authority in England — a council cannot alter them. The ratio for each band:
| Band | Ratio of Band D | England avg 2026-27 |
|---|---|---|
| Band A | 6/9 | £1,594.35/yr |
| Band B | 7/9 | £1,860.07/yr |
| Band C | 8/9 | £2,125.80/yr |
| Band D (source) | 9/9 | £2,391.52/yr |
| Band E | 11/9 | £2,922.97/yr |
| Band F | 13/9 | £3,454.42/yr |
| Band G | 15/9 | £3,985.87/yr |
| Band H | 18/9 | £4,783.04/yr |
- 3Compute the England average for each band using the England aggregate row from the same MHCLG source. England Band D 2026-27: £2,391.52. All other England band averages follow from the statutory ratios above.
- 4Compute GCTBI. For each area × band cell:
GCTBI = (england_band − area_band) / england_band × 100, rounded to 1 decimal place. Positive means cheaper than England average.
Worked examples (Band D, 2026-27)
| Council | Band D | England avg | GCTBI | Interpretation |
|---|---|---|---|---|
| Wandsworth | £1,028.21 | £2,391.52 | +57.0 | 57.0% below England average |
| England | £2,391.52 | £2,391.52 | 0.0 | Baseline (by definition) |
| Dorset Council | £2,765.02 | £2,391.52 | -15.6 | 15.6% above England average |
Coverage and limitations
- 296 billing authorities in England are covered. Scotland, Wales and Northern Ireland publish separate council tax statistics and are not included.
- Band D only is from the source file. Bands A–C and E–H are the legal arithmetic transformation of Band D using the statutory ratios — they are not separately published and are NOT estimates. Every page states this.
- The GCTBI is relative to the England aggregate, not a regional average. A positive GCTBI means cheaper than England, which may still be expensive within a region with uniformly high costs.
- Published annually on the MHCLG council-tax-levels statistics release (typically May each year for the financial year beginning the previous April). The GCTBI on all Gera pages is re-dated on publication of the new MHCLG data.
Explore the index
All 8 band rankings →Contains public sector information published by Ministry of Housing, Communities and Local Government (MHCLG) and licensed under the Open Government Licence v3.0. Source: Council Tax levels set by local authorities in England 2026 to 2027 (MHCLG) (2026-27, published May 2026).