# property.council-tax-band

Every council tax band is charged as a fixed proportion of Band D, set in
statute. The authority publishes its Band D figure each year; this turns it
into the charge for any band:

    charge = Band D × band proportion ÷ Band D proportion

`councilTaxBand(money(200000, "GBP"), "A", "england", "2026-04-01")` is
£1,333.33: six ninths of £2,000.

## The ratios, as dated data

`data/band-ratios.json` holds each nation's proportions with the dates they
apply from:

| nation | from | A | B | C | D | E | F | G | H | I |
|---|---|---|---|---|---|---|---|---|---|---|
| England | 1 April 1993 | 6 | 7 | 8 | 9 | 11 | 13 | 15 | 18 | |
| Wales | 1 April 1993 | 6 | 7 | 8 | 9 | 11 | 13 | 15 | 18 | |
| Wales | 1 April 2005 | 6 | 7 | 8 | 9 | 11 | 13 | 15 | 18 | 21 |
| Scotland | 1 April 1993 | 240 | 280 | 320 | 360 | 440 | 520 | 600 | 720 | |
| Scotland | 1 April 2017 | 240 | 280 | 320 | 360 | 473 | 585 | 705 | 882 | |

England and Wales are ninths of Band D; Scotland is written in 360ths. Band I
exists only in Wales, from the 2005 revaluation; asking for it elsewhere, or
for a band before it existed, is an error. Scotland's 2017 change raised
bands E to H only.

Pass any date inside the financial year (1 April to 31 March) being charged.

## Rounding

The exact fraction is rounded half-up to the penny, once. Authorities differ
in how they round instalments; that is not this function's job.

## What it does not do

Discounts (the 25% single person discount), exemptions, disabled band
reduction, premiums on empty and second homes, and splitting the charge
into instalments. Northern Ireland has domestic rates, not council tax.

## Sources

- Local Government Finance Act 1992, section 5(1) (England: 6:7:8:9:11:13:15:18)
  and 5(1A) (Wales, for financial years beginning on or after 1 April 2005:
  6:7:8:9:11:13:15:18:21): https://www.legislation.gov.uk/ukpga/1992/14/section/5
- Local Government Finance Act 1992, section 74(1) (Scotland:
  240:280:320:360:473:585:705:882): https://www.legislation.gov.uk/ukpga/1992/14/section/74
- The Council Tax (Substitution of Proportion) (Scotland) Order 2016 (SSI
  2016/368), for financial years beginning on or after 1 April 2017, the
  first change to the Scottish proportion since 1992:
  https://www.legislation.gov.uk/ssi/2016/368/made . The pre-2017 Scottish
  row (240:280:320:360:440:520:600:720) is the original 1992 proportion
  expressed in 360ths, identical to England's 6:7:8:9:11:13:15:18.

1.0.1 fixes Python accepting a trailing newline or non-ASCII digits in onDate; adds tests.