diff --git a/changelog.d/council-tax-computed-liability.added.md b/changelog.d/council-tax-computed-liability.added.md
new file mode 100644
index 0000000000..f91130b7ac
--- /dev/null
+++ b/changelog.d/council-tax-computed-liability.added.md
@@ -0,0 +1 @@
+Add council_tax_band_d_amount and simulated_council_tax, computing gross council tax from local authority Band D amounts and statutory band ratios. Band D amounts cover all 350 April 2023 local authorities across England, Wales and Scotland for fiscal 2025 and 2026.
diff --git a/policyengine_uk/parameters/gov/local_authorities/council_tax/band_d/amounts.yaml b/policyengine_uk/parameters/gov/local_authorities/council_tax/band_d/amounts.yaml
new file mode 100644
index 0000000000..ece88c9e18
--- /dev/null
+++ b/policyengine_uk/parameters/gov/local_authorities/council_tax/band_d/amounts.yaml
@@ -0,0 +1,1066 @@
+description: Band D council tax amount set by each local authority, before any discounts, exemptions or Council Tax Reduction. For England and Wales this is the area figure for the billing authority, so it includes the county, police, fire, combined authority and parish or community council precepts as well as the billing authority's own charge; for Scotland it is the council's Band D rate, which excludes the separately billed water and waste water charges.
+metadata:
+  economy: false
+  propagate_metadata_to_children: true
+  unit: currency-GBP
+  period: year
+  label: Local authority Band D council tax amount
+  reference:
+    - title: "England 2026-27: Council tax levels set by local authorities in England, Table 10 local authority level data, sheet Data_Billing, line 17 (average Band D 2 adult equivalent council tax for the area of the billing authority, including both local and major precepts)"
+      href: https://assets.publishing.service.gov.uk/media/6a02eeeccd2e0e8b5b20b449/Table_10_2026-27.ods
+    - title: "England 2025-26: Council tax levels set by local authorities in England, Table 10 local authority level data (revised), sheet Data_Billing, line 17 (same area basis)"
+      href: https://assets.publishing.service.gov.uk/media/6a02f143e71c4cdf4026ba48/Table_10_2025-26.ods
+    - title: "Wales 2026-27 and 2025-26: Council tax levels April 2026 to March 2027, associated data tables, Table 1 column 'Overall average band D' (county council, community council and police authority elements combined); Table 2 carries the 2025-26 figure"
+      href: https://gov.wales/sites/default/files/statistics-and-research/2026-03/council-tax-levels-april-2026-march-2027-153478.xlsx
+    - title: "Scotland 2026-27 and 2025-26: Band D council tax 1996-97 to 2026-27, Council Tax datasets (excludes water and waste water charges)"
+      href: https://www.gov.scot/binaries/content/documents/govscot/publications/statistics/2019/04/council-tax-datasets/documents/band-d/band-d-council-tax-1996-97-to-2019-20-data/band-d-council-tax-1996-97-to-2019-20-data/govscot%3Adocument/CTAS%2B2026%2B-%2BCouncil%2BTax%2BAssumptions%2B-%2BBand%2BD%2BCouncil%2BTax%2Brates%2Bby%2Byear%2B-%2B1996-97%2Bto%2B2026-27.xlsx
+ABERDEEN_CITY:
+  2025-01-01: 1636.27
+  2026-01-01: 1747.54
+ABERDEENSHIRE:
+  2025-01-01: 1532.76
+  2026-01-01: 1686.04
+ADUR:
+  2025-01-01: 2432.50
+  2026-01-01: 2548.28
+AMBER_VALLEY:
+  2025-01-01: 2297.98
+  2026-01-01: 2407.69
+ANGUS:
+  2025-01-01: 1461.52
+  2026-01-01: 1598.65
+ARGYLL_AND_BUTE:
+  2025-01-01: 1625.64
+  2026-01-01: 1783.33
+ARUN:
+  2025-01-01: 2371.09
+  2026-01-01: 2487.24
+ASHFIELD:
+  2025-01-01: 2506.63
+  2026-01-01: 2608.76
+ASHFORD:
+  2025-01-01: 2311.19
+  2026-01-01: 2410.16
+BABERGH:
+  2025-01-01: 2233.16
+  2026-01-01: 2341.55
+BARKING_AND_DAGENHAM:
+  2025-01-01: 2098.14
+  2026-01-01: 2198.51
+BARNET:
+  2025-01-01: 2035.52
+  2026-01-01: 2132.60
+BARNSLEY:
+  2025-01-01: 2241.35
+  2026-01-01: 2325.96
+BASILDON:
+  2025-01-01: 2244.63
+  2026-01-01: 2327.24
+BASINGSTOKE_AND_DEANE:
+  2025-01-01: 2147.87
+  2026-01-01: 2255.21
+BASSETLAW:
+  2025-01-01: 2539.53
+  2026-01-01: 2644.95
+BATH_AND_NORTH_EAST_SOMERSET:
+  2025-01-01: 2265.80
+  2026-01-01: 2383.42
+BEDFORD:
+  2025-01-01: 2350.94
+  2026-01-01: 2471.74
+BEXLEY:
+  2025-01-01: 2258.03
+  2026-01-01: 2366.36
+BIRMINGHAM:
+  2025-01-01: 2245.41
+  2026-01-01: 2362.90
+BLABY:
+  2025-01-01: 2406.77
+  2026-01-01: 2490.22
+BLACKBURN_WITH_DARWEN:
+  2025-01-01: 2337.17
+  2026-01-01: 2455.27
+BLACKPOOL:
+  2025-01-01: 2392.21
+  2026-01-01: 2513.22
+BLAENAU_GWENT:
+  2025-01-01: 2428.43
+  2026-01-01: 2531.26
+BOLSOVER:
+  2025-01-01: 2447.51
+  2026-01-01: 2559.41
+BOLTON:
+  2025-01-01: 2266.53
+  2026-01-01: 2399.74
+BOSTON:
+  2025-01-01: 2236.62
+  2026-01-01: 2308.73
+BOURNEMOUTH_CHRISTCHURCH_AND_POOLE:
+  2025-01-01: 2264.78
+  2026-01-01: 2435.58
+BRACKNELL_FOREST:
+  2025-01-01: 2155.21
+  2026-01-01: 2264.80
+BRADFORD:
+  2025-01-01: 2246.15
+  2026-01-01: 2360.73
+BRAINTREE:
+  2025-01-01: 2194.67
+  2026-01-01: 2280.34
+BRECKLAND:
+  2025-01-01: 2328.59
+  2026-01-01: 2443.67
+BRENT:
+  2025-01-01: 2133.15
+  2026-01-01: 2235.27
+BRENTWOOD:
+  2025-01-01: 2166.72
+  2026-01-01: 2258.14
+BRIDGEND:
+  2025-01-01: 2357.63
+  2026-01-01: 2477.99
+BRIGHTON_AND_HOVE:
+  2025-01-01: 2456.78
+  2026-01-01: 2580.54
+BRISTOL_CITY_OF:
+  2025-01-01: 2583.89
+  2026-01-01: 2713.68
+BROADLAND:
+  2025-01-01: 2327.99
+  2026-01-01: 2437.78
+BROMLEY:
+  2025-01-01: 2042.46
+  2026-01-01: 2140.04
+BROMSGROVE:
+  2025-01-01: 2302.72
+  2026-01-01: 2478.65
+BROXBOURNE:
+  2025-01-01: 2198.11
+  2026-01-01: 2306.43
+BROXTOWE:
+  2025-01-01: 2516.20
+  2026-01-01: 2618.21
+BUCKINGHAMSHIRE:
+  2025-01-01: 2401.53
+  2026-01-01: 2526.58
+BURNLEY:
+  2025-01-01: 2455.83
+  2026-01-01: 2549.42
+BURY:
+  2025-01-01: 2414.58
+  2026-01-01: 2555.15
+CAERPHILLY:
+  2025-01-01: 1956.20
+  2026-01-01: 2082.88
+CALDERDALE:
+  2025-01-01: 2302.33
+  2026-01-01: 2420.15
+CAMBRIDGE:
+  2025-01-01: 2355.41
+  2026-01-01: 2467.02
+CAMDEN:
+  2025-01-01: 2106.69
+  2026-01-01: 2207.55
+CANNOCK_CHASE:
+  2025-01-01: 2282.30
+  2026-01-01: 2375.83
+CANTERBURY:
+  2025-01-01: 2321.73
+  2026-01-01: 2419.33
+CARDIFF:
+  2025-01-01: 1926.18
+  2026-01-01: 2013.18
+CARMARTHENSHIRE:
+  2025-01-01: 2232.06
+  2026-01-01: 2351.20
+CASTLE_POINT:
+  2025-01-01: 2227.21
+  2026-01-01: 2318.63
+CENTRAL_BEDFORDSHIRE:
+  2025-01-01: 2394.14
+  2026-01-01: 2516.16
+CEREDIGION:
+  2025-01-01: 2296.09
+  2026-01-01: 2419.45
+CHARNWOOD:
+  2025-01-01: 2327.50
+  2026-01-01: 2405.64
+CHELMSFORD:
+  2025-01-01: 2206.97
+  2026-01-01: 2300.18
+CHELTENHAM:
+  2025-01-01: 2258.28
+  2026-01-01: 2369.52
+CHERWELL:
+  2025-01-01: 2463.87
+  2026-01-01: 2582.96
+CHESHIRE_EAST:
+  2025-01-01: 2332.61
+  2026-01-01: 2454.87
+CHESHIRE_WEST_AND_CHESTER:
+  2025-01-01: 2392.03
+  2026-01-01: 2517.33
+CHESTERFIELD:
+  2025-01-01: 2233.12
+  2026-01-01: 2339.49
+CHICHESTER:
+  2025-01-01: 2346.40
+  2026-01-01: 2469.68
+CHORLEY:
+  2025-01-01: 2342.85
+  2026-01-01: 2430.23
+CITY_OF_EDINBURGH:
+  2025-01-01: 1563.51
+  2026-01-01: 1626.05
+CITY_OF_LONDON:
+  2025-01-01: 1274.07
+  2026-01-01: 1329.56
+CLACKMANNANSHIRE:
+  2025-01-01: 1594.38
+  2026-01-01: 1683.67
+COLCHESTER:
+  2025-01-01: 2192.08
+  2026-01-01: 2282.85
+CONWY:
+  2025-01-01: 2320.83
+  2026-01-01: 2472.82
+CORNWALL:
+  2025-01-01: 2459.92
+  2026-01-01: 2590.93
+COTSWOLD:
+  2025-01-01: 2276.70
+  2026-01-01: 2391.65
+COUNTY_DURHAM:
+  2025-01-01: 2551.17
+  2026-01-01: 2622.15
+COVENTRY:
+  2025-01-01: 2413.68
+  2026-01-01: 2516.72
+CRAWLEY:
+  2025-01-01: 2306.49
+  2026-01-01: 2418.46
+CROYDON:
+  2025-01-01: 2480.48
+  2026-01-01: 2599.91
+CUMBERLAND:
+  2025-01-01: 2393.90
+  2026-01-01: 2511.32
+DACORUM:
+  2025-01-01: 2294.23
+  2026-01-01: 2408.51
+DARLINGTON:
+  2025-01-01: 2371.60
+  2026-01-01: 2493.83
+DARTFORD:
+  2025-01-01: 2280.55
+  2026-01-01: 2375.15
+DENBIGHSHIRE:
+  2025-01-01: 2217.08
+  2026-01-01: 2339.03
+DERBY:
+  2025-01-01: 2195.75
+  2026-01-01: 2306.00
+DERBYSHIRE_DALES:
+  2025-01-01: 2332.42
+  2026-01-01: 2444.70
+DONCASTER:
+  2025-01-01: 2110.50
+  2026-01-01: 2167.75
+DORSET:
+  2025-01-01: 2630.30
+  2026-01-01: 2765.02
+DOVER:
+  2025-01-01: 2364.45
+  2026-01-01: 2461.74
+DUDLEY:
+  2025-01-01: 2038.57
+  2026-01-01: 2144.84
+DUMFRIES_AND_GALLOWAY:
+  2025-01-01: 1454.98
+  2026-01-01: 1578.65
+DUNDEE_CITY:
+  2025-01-01: 1605.34
+  2026-01-01: 1729.69
+EALING:
+  2025-01-01: 2041.02
+  2026-01-01: 2138.53
+EAST_AYRSHIRE:
+  2025-01-01: 1606.44
+  2026-01-01: 1717.28
+EAST_CAMBRIDGESHIRE:
+  2025-01-01: 2374.13
+  2026-01-01: 2485.18
+EAST_DEVON:
+  2025-01-01: 2461.40
+  2026-01-01: 2595.46
+EAST_DUNBARTONSHIRE:
+  2025-01-01: 1599.70
+  2026-01-01: 1751.67
+EAST_HAMPSHIRE:
+  2025-01-01: 2231.64
+  2026-01-01: 2343.92
+EAST_HERTFORDSHIRE:
+  2025-01-01: 2339.63
+  2026-01-01: 2454.78
+EAST_LINDSEY:
+  2025-01-01: 2201.57
+  2026-01-01: 2275.88
+EAST_LOTHIAN:
+  2025-01-01: 1579.18
+  2026-01-01: 1697.62
+EAST_RENFREWSHIRE:
+  2025-01-01: 1528.44
+  2026-01-01: 1620.15
+EAST_RIDING_OF_YORKSHIRE:
+  2025-01-01: 2343.55
+  2026-01-01: 2466.08
+EAST_STAFFORDSHIRE:
+  2025-01-01: 2257.48
+  2026-01-01: 2351.34
+EAST_SUFFOLK:
+  2025-01-01: 2222.36
+  2026-01-01: 2334.80
+EASTBOURNE:
+  2025-01-01: 2532.49
+  2026-01-01: 2654.28
+EASTLEIGH:
+  2025-01-01: 2227.68
+  2026-01-01: 2342.21
+ELMBRIDGE:
+  2025-01-01: 2442.92
+  2026-01-01: 2557.75
+ENFIELD:
+  2025-01-01: 2164.02
+  2026-01-01: 2267.67
+EPPING_FOREST:
+  2025-01-01: 2186.69
+  2026-01-01: 2277.21
+EPSOM_AND_EWELL:
+  2025-01-01: 2416.84
+  2026-01-01: 2530.84
+EREWASH:
+  2025-01-01: 2260.06
+  2026-01-01: 2360.64
+EXETER:
+  2025-01-01: 2379.90
+  2026-01-01: 2495.36
+FALKIRK:
+  2025-01-01: 1576.77
+  2026-01-01: 1715.09
+FAREHAM:
+  2025-01-01: 2164.55
+  2026-01-01: 2270.55
+FENLAND:
+  2025-01-01: 2432.81
+  2026-01-01: 2537.74
+FIFE:
+  2025-01-01: 1498.76
+  2026-01-01: 1573.70
+FLINTSHIRE:
+  2025-01-01: 2246.47
+  2026-01-01: 2376.17
+FOLKESTONE_AND_HYTHE:
+  2025-01-01: 2437.35
+  2026-01-01: 2538.75
+FOREST_OF_DEAN:
+  2025-01-01: 2326.88
+  2026-01-01: 2443.42
+FYLDE:
+  2025-01-01: 2387.78
+  2026-01-01: 2483.94
+GATESHEAD:
+  2025-01-01: 2578.46
+  2026-01-01: 2715.81
+GEDLING:
+  2025-01-01: 2507.09
+  2026-01-01: 2609.55
+GLASGOW_CITY:
+  2025-01-01: 1611.00
+  2026-01-01: 1706.00
+GLOUCESTER:
+  2025-01-01: 2246.16
+  2026-01-01: 2355.84
+GOSPORT:
+  2025-01-01: 2236.14
+  2026-01-01: 2344.29
+GRAVESHAM:
+  2025-01-01: 2313.06
+  2026-01-01: 2408.24
+GREAT_YARMOUTH:
+  2025-01-01: 2305.13
+  2026-01-01: 2414.41
+GREENWICH:
+  2025-01-01: 2011.81
+  2026-01-01: 2107.86
+GUILDFORD:
+  2025-01-01: 2428.89
+  2026-01-01: 2547.30
+GWYNEDD:
+  2025-01-01: 2340.22
+  2026-01-01: 2468.77
+HACKNEY:
+  2025-01-01: 1966.51
+  2026-01-01: 2060.30
+HALTON:
+  2025-01-01: 2249.34
+  2026-01-01: 2366.61
+HAMMERSMITH_AND_FULHAM:
+  2025-01-01: 1451.42
+  2026-01-01: 1519.51
+HARBOROUGH:
+  2025-01-01: 2324.96
+  2026-01-01: 2389.87
+HARINGEY:
+  2025-01-01: 2207.94
+  2026-01-01: 2313.78
+HARLOW:
+  2025-01-01: 2216.43
+  2026-01-01: 2298.69
+HARROW:
+  2025-01-01: 2395.86
+  2026-01-01: 2511.07
+HART:
+  2025-01-01: 2285.15
+  2026-01-01: 2400.02
+HARTLEPOOL:
+  2025-01-01: 2498.53
+  2026-01-01: 2560.20
+HASTINGS:
+  2025-01-01: 2554.14
+  2026-01-01: 2676.58
+HAVANT:
+  2025-01-01: 2212.89
+  2026-01-01: 2320.28
+HAVERING:
+  2025-01-01: 2313.55
+  2026-01-01: 2424.66
+HEREFORDSHIRE_COUNTY_OF:
+  2025-01-01: 2449.17
+  2026-01-01: 2574.37
+HERTSMERE:
+  2025-01-01: 2289.22
+  2026-01-01: 2405.83
+HIGH_PEAK:
+  2025-01-01: 2275.52
+  2026-01-01: 2384.66
+HIGHLAND:
+  2025-01-01: 1527.09
+  2026-01-01: 1633.99
+HILLINGDON:
+  2025-01-01: 1952.38
+  2026-01-01: 2045.46
+HINCKLEY_AND_BOSWORTH:
+  2025-01-01: 2304.14
+  2026-01-01: 2382.62
+HORSHAM:
+  2025-01-01: 2321.54
+  2026-01-01: 2441.01
+HOUNSLOW:
+  2025-01-01: 2085.82
+  2026-01-01: 2185.56
+HUNTINGDONSHIRE:
+  2025-01-01: 2439.67
+  2026-01-01: 2556.40
+HYNDBURN:
+  2025-01-01: 2380.02
+  2026-01-01: 2465.98
+INVERCLYDE:
+  2025-01-01: 1551.30
+  2026-01-01: 1673.85
+IPSWICH:
+  2025-01-01: 2358.54
+  2026-01-01: 2468.25
+ISLE_OF_ANGLESEY:
+  2025-01-01: 2143.94
+  2026-01-01: 2260.73
+ISLE_OF_WIGHT:
+  2025-01-01: 2493.36
+  2026-01-01: 2625.79
+ISLES_OF_SCILLY:
+  2025-01-01: 1950.03
+  2026-01-01: 2047.96
+ISLINGTON:
+  2025-01-01: 2012.10
+  2026-01-01: 2108.15
+KENSINGTON_AND_CHELSEA:
+  2025-01-01: 1591.59
+  2026-01-01: 1666.65
+KINGS_LYNN_AND_WEST_NORFOLK:
+  2025-01-01: 2318.63
+  2026-01-01: 2430.13
+KINGSTON_UPON_HULL_CITY_OF:
+  2025-01-01: 2182.52
+  2026-01-01: 2295.04
+KINGSTON_UPON_THAMES:
+  2025-01-01: 2489.34
+  2026-01-01: 2609.20
+KIRKLEES:
+  2025-01-01: 2321.76
+  2026-01-01: 2441.07
+KNOWSLEY:
+  2025-01-01: 2371.28
+  2026-01-01: 2488.25
+LAMBETH:
+  2025-01-01: 1953.95
+  2026-01-01: 2047.11
+LANCASTER:
+  2025-01-01: 2407.50
+  2026-01-01: 2503.19
+LEEDS:
+  2025-01-01: 2172.39
+  2026-01-01: 2283.73
+LEICESTER:
+  2025-01-01: 2407.72
+  2026-01-01: 2528.75
+LEWES:
+  2025-01-01: 2627.39
+  2026-01-01: 2756.17
+LEWISHAM:
+  2025-01-01: 2135.13
+  2026-01-01: 2237.33
+LICHFIELD:
+  2025-01-01: 2259.21
+  2026-01-01: 2351.90
+LINCOLN:
+  2025-01-01: 2260.98
+  2026-01-01: 2323.08
+LIVERPOOL:
+  2025-01-01: 2546.45
+  2026-01-01: 2673.59
+LUTON:
+  2025-01-01: 2320.43
+  2026-01-01: 2439.93
+MAIDSTONE:
+  2025-01-01: 2403.78
+  2026-01-01: 2502.59
+MALDON:
+  2025-01-01: 2232.83
+  2026-01-01: 2328.37
+MALVERN_HILLS:
+  2025-01-01: 2280.82
+  2026-01-01: 2450.92
+MANCHESTER:
+  2025-01-01: 2183.03
+  2026-01-01: 2312.04
+MANSFIELD:
+  2025-01-01: 2498.40
+  2026-01-01: 2600.38
+MEDWAY:
+  2025-01-01: 2215.38
+  2026-01-01: 2328.55
+MELTON:
+  2025-01-01: 2350.68
+  2026-01-01: 2429.67
+MERTHYR_TYDFIL:
+  2025-01-01: 2464.01
+  2026-01-01: 2593.60
+MERTON:
+  2025-01-01: 2094.43
+  2026-01-01: 2146.76
+MID_DEVON:
+  2025-01-01: 2521.17
+  2026-01-01: 2656.41
+MID_SUFFOLK:
+  2025-01-01: 2208.43
+  2026-01-01: 2316.88
+MID_SUSSEX:
+  2025-01-01: 2356.49
+  2026-01-01: 2474.26
+MIDDLESBROUGH:
+  2025-01-01: 2487.65
+  2026-01-01: 2549.16
+MIDLOTHIAN:
+  2025-01-01: 1666.20
+  2026-01-01: 1816.16
+MILTON_KEYNES:
+  2025-01-01: 2257.98
+  2026-01-01: 2372.21
+MOLE_VALLEY:
+  2025-01-01: 2405.75
+  2026-01-01: 2519.86
+MONMOUTHSHIRE:
+  2025-01-01: 2277.19
+  2026-01-01: 2416.50
+MORAY:
+  2025-01-01: 1573.76
+  2026-01-01: 1731.14
+NA_H_EILEANAN_SIAR:
+  2025-01-01: 1387.56
+  2026-01-01: 1505.50
+NEATH_PORT_TALBOT:
+  2025-01-01: 2440.78
+  2026-01-01: 2541.39
+NEW_FOREST:
+  2025-01-01: 2303.37
+  2026-01-01: 2419.76
+NEWARK_AND_SHERWOOD:
+  2025-01-01: 2582.22
+  2026-01-01: 2682.10
+NEWCASTLE_UNDER_LYME:
+  2025-01-01: 2244.85
+  2026-01-01: 2334.25
+NEWCASTLE_UPON_TYNE:
+  2025-01-01: 2413.15
+  2026-01-01: 2542.19
+NEWHAM:
+  2025-01-01: 1855.96
+  2026-01-01: 1944.23
+NEWPORT:
+  2025-01-01: 1983.97
+  2026-01-01: 2088.48
+NORTH_AYRSHIRE:
+  2025-01-01: 1553.77
+  2026-01-01: 1685.84
+NORTH_DEVON:
+  2025-01-01: 2514.66
+  2026-01-01: 2642.21
+NORTH_EAST_DERBYSHIRE:
+  2025-01-01: 2354.93
+  2026-01-01: 2466.57
+NORTH_EAST_LINCOLNSHIRE:
+  2025-01-01: 2371.01
+  2026-01-01: 2483.85
+NORTH_HERTFORDSHIRE:
+  2025-01-01: 2332.61
+  2026-01-01: 2448.52
+NORTH_KESTEVEN:
+  2025-01-01: 2261.06
+  2026-01-01: 2337.81
+NORTH_LANARKSHIRE:
+  2025-01-01: 1452.86
+  2026-01-01: 1554.56
+NORTH_LINCOLNSHIRE:
+  2025-01-01: 2238.09
+  2026-01-01: 2348.46
+NORTH_NORFOLK:
+  2025-01-01: 2341.13
+  2026-01-01: 2459.93
+NORTH_NORTHAMPTONSHIRE:
+  2025-01-01: 2301.93
+  2026-01-01: 2423.96
+NORTH_SOMERSET:
+  2025-01-01: 2294.94
+  2026-01-01: 2491.22
+NORTH_TYNESIDE:
+  2025-01-01: 2336.45
+  2026-01-01: 2461.77
+NORTH_WARWICKSHIRE:
+  2025-01-01: 2431.78
+  2026-01-01: 2532.10
+NORTH_WEST_LEICESTERSHIRE:
+  2025-01-01: 2338.10
+  2026-01-01: 2418.20
+NORTH_YORKSHIRE:
+  2025-01-01: 2418.26
+  2026-01-01: 2544.34
+NORTHUMBERLAND:
+  2025-01-01: 2464.63
+  2026-01-01: 2596.94
+NORWICH:
+  2025-01-01: 2391.59
+  2026-01-01: 2503.44
+NOTTINGHAM:
+  2025-01-01: 2656.19
+  2026-01-01: 2755.39
+NUNEATON_AND_BEDWORTH:
+  2025-01-01: 2398.13
+  2026-01-01: 2502.16
+OADBY_AND_WIGSTON:
+  2025-01-01: 2330.02
+  2026-01-01: 2406.85
+OLDHAM:
+  2025-01-01: 2459.40
+  2026-01-01: 2602.23
+ORKNEY_ISLANDS:
+  2025-01-01: 1574.60
+  2026-01-01: 1669.07
+OXFORD:
+  2025-01-01: 2557.13
+  2026-01-01: 2678.40
+PEMBROKESHIRE:
+  2025-01-01: 2059.82
+  2026-01-01: 2166.15
+PENDLE:
+  2025-01-01: 2535.19
+  2026-01-01: 2640.18
+PERTH_AND_KINROSS:
+  2025-01-01: 1537.04
+  2026-01-01: 1673.84
+PETERBOROUGH:
+  2025-01-01: 2185.72
+  2026-01-01: 2293.47
+PLYMOUTH:
+  2025-01-01: 2325.42
+  2026-01-01: 2441.85
+PORTSMOUTH:
+  2025-01-01: 2180.92
+  2026-01-01: 2291.71
+POWYS:
+  2025-01-01: 2234.44
+  2026-01-01: 2351.72
+PRESTON:
+  2025-01-01: 2477.85
+  2026-01-01: 2575.74
+READING:
+  2025-01-01: 2487.11
+  2026-01-01: 2612.77
+REDBRIDGE:
+  2025-01-01: 2189.67
+  2026-01-01: 2294.58
+REDCAR_AND_CLEVELAND:
+  2025-01-01: 2424.47
+  2026-01-01: 2544.48
+REDDITCH:
+  2025-01-01: 2289.33
+  2026-01-01: 2462.95
+REIGATE_AND_BANSTEAD:
+  2025-01-01: 2459.20
+  2026-01-01: 2566.61
+RENFREWSHIRE:
+  2025-01-01: 1572.61
+  2026-01-01: 1690.56
+RHONDDA_CYNON_TAF:
+  2025-01-01: 2190.10
+  2026-01-01: 2289.43
+RIBBLE_VALLEY:
+  2025-01-01: 2299.58
+  2026-01-01: 2386.50
+RICHMOND_UPON_THAMES:
+  2025-01-01: 2372.07
+  2026-01-01: 2486.10
+ROCHDALE:
+  2025-01-01: 2458.09
+  2026-01-01: 2600.83
+ROCHFORD:
+  2025-01-01: 2268.00
+  2026-01-01: 2363.48
+ROSSENDALE:
+  2025-01-01: 2424.37
+  2026-01-01: 2519.97
+ROTHER:
+  2025-01-01: 2561.29
+  2026-01-01: 2700.95
+ROTHERHAM:
+  2025-01-01: 2283.26
+  2026-01-01: 2381.53
+RUGBY:
+  2025-01-01: 2378.04
+  2026-01-01: 2483.05
+RUNNYMEDE:
+  2025-01-01: 2380.06
+  2026-01-01: 2492.99
+RUSHCLIFFE:
+  2025-01-01: 2531.50
+  2026-01-01: 2643.27
+RUSHMOOR:
+  2025-01-01: 2212.82
+  2026-01-01: 2320.28
+RUTLAND:
+  2025-01-01: 2671.01
+  2026-01-01: 2737.58
+SALFORD:
+  2025-01-01: 2452.02
+  2026-01-01: 2594.45
+SANDWELL:
+  2025-01-01: 2133.45
+  2026-01-01: 2244.46
+SCOTTISH_BORDERS:
+  2025-01-01: 1491.72
+  2026-01-01: 1618.52
+SEFTON:
+  2025-01-01: 2460.92
+  2026-01-01: 2583.22
+SEVENOAKS:
+  2025-01-01: 2419.44
+  2026-01-01: 2522.36
+SHEFFIELD:
+  2025-01-01: 2388.76
+  2026-01-01: 2510.16
+SHETLAND_ISLANDS:
+  2025-01-01: 1386.67
+  2026-01-01: 1487.90
+SHROPSHIRE:
+  2025-01-01: 2318.80
+  2026-01-01: 2528.18
+SLOUGH:
+  2025-01-01: 2298.55
+  2026-01-01: 2414.44
+SOLIHULL:
+  2025-01-01: 2087.81
+  2026-01-01: 2197.26
+SOMERSET:
+  2025-01-01: 2438.62
+  2026-01-01: 2560.59
+SOUTH_AYRSHIRE:
+  2025-01-01: 1569.41
+  2026-01-01: 1694.96
+SOUTH_CAMBRIDGESHIRE:
+  2025-01-01: 2414.52
+  2026-01-01: 2536.25
+SOUTH_DERBYSHIRE:
+  2025-01-01: 2231.86
+  2026-01-01: 2339.61
+SOUTH_GLOUCESTERSHIRE:
+  2025-01-01: 2427.90
+  2026-01-01: 2550.59
+SOUTH_HAMS:
+  2025-01-01: 2491.75
+  2026-01-01: 2615.22
+SOUTH_HOLLAND:
+  2025-01-01: 2205.31
+  2026-01-01: 2278.20
+SOUTH_KESTEVEN:
+  2025-01-01: 2186.95
+  2026-01-01: 2260.00
+SOUTH_LANARKSHIRE:
+  2025-01-01: 1378.85
+  2026-01-01: 1468.47
+SOUTH_NORFOLK:
+  2025-01-01: 2367.89
+  2026-01-01: 2482.87
+SOUTH_OXFORDSHIRE:
+  2025-01-01: 2474.44
+  2026-01-01: 2597.57
+SOUTH_RIBBLE:
+  2025-01-01: 2352.12
+  2026-01-01: 2442.66
+SOUTH_STAFFORDSHIRE:
+  2025-01-01: 2219.66
+  2026-01-01: 2313.67
+SOUTH_TYNESIDE:
+  2025-01-01: 2311.18
+  2026-01-01: 2434.43
+SOUTHAMPTON:
+  2025-01-01: 2266.44
+  2026-01-01: 2381.48
+SOUTHEND_ON_SEA:
+  2025-01-01: 2154.65
+  2026-01-01: 2265.17
+SOUTHWARK:
+  2025-01-01: 1877.90
+  2026-01-01: 1967.26
+SPELTHORNE:
+  2025-01-01: 2412.78
+  2026-01-01: 2526.44
+ST_ALBANS:
+  2025-01-01: 2305.95
+  2026-01-01: 2419.22
+ST_HELENS:
+  2025-01-01: 2288.53
+  2026-01-01: 2403.38
+STAFFORD:
+  2025-01-01: 2210.78
+  2026-01-01: 2302.68
+STAFFORDSHIRE_MOORLANDS:
+  2025-01-01: 2240.43
+  2026-01-01: 2338.21
+STEVENAGE:
+  2025-01-01: 2281.28
+  2026-01-01: 2391.97
+STIRLING:
+  2025-01-01: 1611.78
+  2026-01-01: 1752.87
+STOCKPORT:
+  2025-01-01: 2475.31
+  2026-01-01: 2618.90
+STOCKTON_ON_TEES:
+  2025-01-01: 2468.74
+  2026-01-01: 2589.83
+STOKE_ON_TRENT:
+  2025-01-01: 2078.34
+  2026-01-01: 2183.12
+STRATFORD_ON_AVON:
+  2025-01-01: 2379.91
+  2026-01-01: 2484.17
+STROUD:
+  2025-01-01: 2369.37
+  2026-01-01: 2491.36
+SUNDERLAND:
+  2025-01-01: 2092.79
+  2026-01-01: 2197.14
+SURREY_HEATH:
+  2025-01-01: 2467.86
+  2026-01-01: 2585.16
+SUTTON:
+  2025-01-01: 2269.72
+  2026-01-01: 2378.64
+SWALE:
+  2025-01-01: 2305.72
+  2026-01-01: 2405.65
+SWANSEA:
+  2025-01-01: 2142.88
+  2026-01-01: 2238.29
+SWINDON:
+  2025-01-01: 2317.63
+  2026-01-01: 2438.10
+TAMESIDE:
+  2025-01-01: 2311.80
+  2026-01-01: 2447.21
+TAMWORTH:
+  2025-01-01: 2209.81
+  2026-01-01: 2300.76
+TANDRIDGE:
+  2025-01-01: 2471.62
+  2026-01-01: 2594.85
+TEIGNBRIDGE:
+  2025-01-01: 2512.83
+  2026-01-01: 2643.12
+TELFORD_AND_WREKIN:
+  2025-01-01: 2146.19
+  2026-01-01: 2256.26
+TENDRING:
+  2025-01-01: 2178.46
+  2026-01-01: 2269.63
+TEST_VALLEY:
+  2025-01-01: 2196.53
+  2026-01-01: 2305.52
+TEWKESBURY:
+  2025-01-01: 2226.55
+  2026-01-01: 2340.53
+THANET:
+  2025-01-01: 2391.23
+  2026-01-01: 2490.90
+THREE_RIVERS:
+  2025-01-01: 2306.47
+  2026-01-01: 2422.31
+THURROCK:
+  2025-01-01: 2145.06
+  2026-01-01: 2254.68
+TONBRIDGE_AND_MALLING:
+  2025-01-01: 2374.77
+  2026-01-01: 2471.83
+TORBAY:
+  2025-01-01: 2350.64
+  2026-01-01: 2470.25
+TORFAEN:
+  2025-01-01: 2059.50
+  2026-01-01: 2155.68
+TORRIDGE:
+  2025-01-01: 2479.12
+  2026-01-01: 2601.42
+TOWER_HAMLETS:
+  2025-01-01: 1754.57
+  2026-01-01: 1837.78
+TRAFFORD:
+  2025-01-01: 2122.54
+  2026-01-01: 2291.70
+TUNBRIDGE_WELLS:
+  2025-01-01: 2347.20
+  2026-01-01: 2446.15
+UTTLESFORD:
+  2025-01-01: 2237.45
+  2026-01-01: 2333.82
+VALE_OF_GLAMORGAN:
+  2025-01-01: 2093.96
+  2026-01-01: 2231.54
+VALE_OF_WHITE_HORSE:
+  2025-01-01: 2456.82
+  2026-01-01: 2577.44
+WAKEFIELD:
+  2025-01-01: 2185.93
+  2026-01-01: 2296.89
+WALSALL:
+  2025-01-01: 2498.27
+  2026-01-01: 2627.48
+WALTHAM_FOREST:
+  2025-01-01: 2277.65
+  2026-01-01: 2386.96
+WANDSWORTH:
+  2025-01-01: 997.75
+  2026-01-01: 1028.21
+WARRINGTON:
+  2025-01-01: 2281.40
+  2026-01-01: 2447.61
+WARWICK:
+  2025-01-01: 2356.53
+  2026-01-01: 2461.55
+WATFORD:
+  2025-01-01: 2343.38
+  2026-01-01: 2446.70
+WAVERLEY:
+  2025-01-01: 2483.85
+  2026-01-01: 2604.87
+WEALDEN:
+  2025-01-01: 2608.44
+  2026-01-01: 2728.43
+WELWYN_HATFIELD:
+  2025-01-01: 2333.46
+  2026-01-01: 2452.26
+WEST_BERKSHIRE:
+  2025-01-01: 2382.84
+  2026-01-01: 2505.37
+WEST_DEVON:
+  2025-01-01: 2574.29
+  2026-01-01: 2705.33
+WEST_DUNBARTONSHIRE:
+  2025-01-01: 1559.86
+  2026-01-01: 1681.53
+WEST_LANCASHIRE:
+  2025-01-01: 2362.12
+  2026-01-01: 2456.23
+WEST_LINDSEY:
+  2025-01-01: 2279.77
+  2026-01-01: 2354.25
+WEST_LOTHIAN:
+  2025-01-01: 1515.45
+  2026-01-01: 1627.59
+WEST_NORTHAMPTONSHIRE:
+  2025-01-01: 2362.51
+  2026-01-01: 2486.66
+WEST_OXFORDSHIRE:
+  2025-01-01: 2443.88
+  2026-01-01: 2566.95
+WEST_SUFFOLK:
+  2025-01-01: 2243.00
+  2026-01-01: 2351.47
+WESTMINSTER:
+  2025-01-01: 1019.00
+  2026-01-01: 1049.55
+WESTMORLAND_AND_FURNESS:
+  2025-01-01: 2389.00
+  2026-01-01: 2507.99
+WIGAN:
+  2025-01-01: 2031.28
+  2026-01-01: 2152.68
+WILTSHIRE:
+  2025-01-01: 2443.40
+  2026-01-01: 2571.78
+WINCHESTER:
+  2025-01-01: 2251.22
+  2026-01-01: 2359.76
+WINDSOR_AND_MAIDENHEAD:
+  2025-01-01: 1823.50
+  2026-01-01: 1952.62
+WIRRAL:
+  2025-01-01: 2381.66
+  2026-01-01: 2500.59
+WOKING:
+  2025-01-01: 2482.03
+  2026-01-01: 2598.04
+WOKINGHAM:
+  2025-01-01: 2376.11
+  2026-01-01: 2497.70
+WOLVERHAMPTON:
+  2025-01-01: 2413.98
+  2026-01-01: 2538.99
+WORCESTER:
+  2025-01-01: 2233.93
+  2026-01-01: 2405.81
+WORTHING:
+  2025-01-01: 2343.12
+  2026-01-01: 2456.13
+WREXHAM:
+  2025-01-01: 2192.89
+  2026-01-01: 2308.88
+WYCHAVON:
+  2025-01-01: 2200.98
+  2026-01-01: 2373.19
+WYRE:
+  2025-01-01: 2365.73
+  2026-01-01: 2460.53
+WYRE_FOREST:
+  2025-01-01: 2327.49
+  2026-01-01: 2512.47
+YORK:
+  2025-01-01: 2175.05
+  2026-01-01: 2287.15
diff --git a/policyengine_uk/parameters/gov/local_authorities/council_tax/band_ratios/england.yaml b/policyengine_uk/parameters/gov/local_authorities/council_tax/band_ratios/england.yaml
new file mode 100644
index 0000000000..f6b6a001b6
--- /dev/null
+++ b/policyengine_uk/parameters/gov/local_authorities/council_tax/band_ratios/england.yaml
@@ -0,0 +1,26 @@
+description: Statutory council tax band proportions for England, relative to Band D.
+metadata:
+  economy: false
+  propagate_metadata_to_children: true
+  unit: /1
+  period: year
+  label: England council tax band ratios
+  reference:
+    - title: Local Government Finance Act 1992, section 5
+      href: https://www.legislation.gov.uk/ukpga/1992/14/section/5
+A:
+  1993-04-01: 0.666666667  # 2/3
+B:
+  1993-04-01: 0.777777778  # 7/9
+C:
+  1993-04-01: 0.888888889  # 8/9
+D:
+  1993-04-01: 1.000000000  # 1/1
+E:
+  1993-04-01: 1.222222222  # 11/9
+F:
+  1993-04-01: 1.444444444  # 13/9
+G:
+  1993-04-01: 1.666666667  # 5/3
+H:
+  1993-04-01: 2.000000000  # 2/1
diff --git a/policyengine_uk/parameters/gov/local_authorities/council_tax/band_ratios/scotland.yaml b/policyengine_uk/parameters/gov/local_authorities/council_tax/band_ratios/scotland.yaml
new file mode 100644
index 0000000000..373236e552
--- /dev/null
+++ b/policyengine_uk/parameters/gov/local_authorities/council_tax/band_ratios/scotland.yaml
@@ -0,0 +1,32 @@
+description: Statutory council tax band proportions for Scotland, relative to Band D. Bands A to D have been unchanged since 1993; SSI 2016/368 substituted a new proportion in section 74(1) of the Local Government Finance Act 1992, raising bands E to H with effect for financial years beginning on or after 1 April 2017.
+metadata:
+  economy: false
+  propagate_metadata_to_children: true
+  unit: /1
+  period: year
+  label: Scotland council tax band ratios
+  reference:
+    - title: Local Government Finance Act 1992, section 74 (proportion 6:7:8:9:11:13:15:18 as originally enacted)
+      href: https://www.legislation.gov.uk/ukpga/1992/14/section/74/enacted
+    - title: The Council Tax (Substitution of Proportion) (Scotland) Order 2016 (SSI 2016/368), article 2 (proportion 240:280:320:360:473:585:705:882 for financial years from 1 April 2017)
+      href: https://www.legislation.gov.uk/ssi/2016/368/article/2/made
+A:
+  1993-04-01: 0.666666667  # 6/9, and 240/360 from 2017
+B:
+  1993-04-01: 0.777777778  # 7/9, and 280/360 from 2017
+C:
+  1993-04-01: 0.888888889  # 8/9, and 320/360 from 2017
+D:
+  1993-04-01: 1.000000000  # 9/9, and 360/360 from 2017
+E:
+  1993-04-01: 1.222222222  # 11/9
+  2017-04-01: 1.313888889  # 473/360
+F:
+  1993-04-01: 1.444444444  # 13/9
+  2017-04-01: 1.625000000  # 585/360
+G:
+  1993-04-01: 1.666666667  # 15/9
+  2017-04-01: 1.958333333  # 705/360
+H:
+  1993-04-01: 2.000000000  # 18/9
+  2017-04-01: 2.450000000  # 882/360
diff --git a/policyengine_uk/parameters/gov/local_authorities/council_tax/band_ratios/wales.yaml b/policyengine_uk/parameters/gov/local_authorities/council_tax/band_ratios/wales.yaml
new file mode 100644
index 0000000000..d2a2ebc330
--- /dev/null
+++ b/policyengine_uk/parameters/gov/local_authorities/council_tax/band_ratios/wales.yaml
@@ -0,0 +1,30 @@
+description: Statutory council tax band proportions for Wales, relative to Band D. Wales has nine bands (A to I) from 1 April 2005.
+metadata:
+  economy: false
+  propagate_metadata_to_children: true
+  unit: /1
+  period: year
+  label: Wales council tax band ratios
+  reference:
+    - title: Local Government Finance Act 1992, section 5
+      href: https://www.legislation.gov.uk/ukpga/1992/14/section/5
+    - title: The Council Tax (Valuation Bands) (Wales) Order 2003
+      href: https://www.legislation.gov.uk/wsi/2003/3046/made
+A:
+  2005-04-01: 0.666666667  # 2/3
+B:
+  2005-04-01: 0.777777778  # 7/9
+C:
+  2005-04-01: 0.888888889  # 8/9
+D:
+  2005-04-01: 1.000000000  # 1/1
+E:
+  2005-04-01: 1.222222222  # 11/9
+F:
+  2005-04-01: 1.444444444  # 13/9
+G:
+  2005-04-01: 1.666666667  # 5/3
+H:
+  2005-04-01: 2.000000000  # 2/1
+I:
+  2005-04-01: 2.333333333  # 7/3
diff --git a/policyengine_uk/tests/policy/baseline/gov/local_authorities/council_tax/simulated_council_tax.yaml b/policyengine_uk/tests/policy/baseline/gov/local_authorities/council_tax/simulated_council_tax.yaml
new file mode 100644
index 0000000000..f736d70c19
--- /dev/null
+++ b/policyengine_uk/tests/policy/baseline/gov/local_authorities/council_tax/simulated_council_tax.yaml
@@ -0,0 +1,438 @@
+- name: England Band A is 2/3 of the Maidstone Band D amount
+  period: 2026
+  absolute_error_margin: 0.01
+  input:
+    people:
+      person:
+        age: 40
+    benunits:
+      benunit:
+        members: [person]
+    households:
+      household:
+        members: [person]
+        region: SOUTH_EAST
+        local_authority: MAIDSTONE
+        council_tax_band: A
+  output:
+    council_tax_band_d_amount: 2502.59
+    simulated_council_tax: 1668.39
+
+- name: England Band B is 7/9 of the Maidstone Band D amount
+  period: 2026
+  absolute_error_margin: 0.01
+  input:
+    people:
+      person:
+        age: 40
+    benunits:
+      benunit:
+        members: [person]
+    households:
+      household:
+        members: [person]
+        region: SOUTH_EAST
+        local_authority: MAIDSTONE
+        council_tax_band: B
+  output:
+    council_tax_band_d_amount: 2502.59
+    simulated_council_tax: 1946.46
+
+- name: England Band C is 8/9 of the Maidstone Band D amount
+  period: 2026
+  absolute_error_margin: 0.01
+  input:
+    people:
+      person:
+        age: 40
+    benunits:
+      benunit:
+        members: [person]
+    households:
+      household:
+        members: [person]
+        region: SOUTH_EAST
+        local_authority: MAIDSTONE
+        council_tax_band: C
+  output:
+    council_tax_band_d_amount: 2502.59
+    simulated_council_tax: 2224.52
+
+- name: England Band D is 1/1 of the Maidstone Band D amount
+  period: 2026
+  absolute_error_margin: 0.01
+  input:
+    people:
+      person:
+        age: 40
+    benunits:
+      benunit:
+        members: [person]
+    households:
+      household:
+        members: [person]
+        region: SOUTH_EAST
+        local_authority: MAIDSTONE
+        council_tax_band: D
+  output:
+    council_tax_band_d_amount: 2502.59
+    simulated_council_tax: 2502.59
+
+- name: England Band E is 11/9 of the Maidstone Band D amount
+  period: 2026
+  absolute_error_margin: 0.01
+  input:
+    people:
+      person:
+        age: 40
+    benunits:
+      benunit:
+        members: [person]
+    households:
+      household:
+        members: [person]
+        region: SOUTH_EAST
+        local_authority: MAIDSTONE
+        council_tax_band: E
+  output:
+    council_tax_band_d_amount: 2502.59
+    simulated_council_tax: 3058.72
+
+- name: England Band F is 13/9 of the Maidstone Band D amount
+  period: 2026
+  absolute_error_margin: 0.01
+  input:
+    people:
+      person:
+        age: 40
+    benunits:
+      benunit:
+        members: [person]
+    households:
+      household:
+        members: [person]
+        region: SOUTH_EAST
+        local_authority: MAIDSTONE
+        council_tax_band: F
+  output:
+    council_tax_band_d_amount: 2502.59
+    simulated_council_tax: 3614.85
+
+- name: England Band G is 5/3 of the Maidstone Band D amount
+  period: 2026
+  absolute_error_margin: 0.01
+  input:
+    people:
+      person:
+        age: 40
+    benunits:
+      benunit:
+        members: [person]
+    households:
+      household:
+        members: [person]
+        region: SOUTH_EAST
+        local_authority: MAIDSTONE
+        council_tax_band: G
+  output:
+    council_tax_band_d_amount: 2502.59
+    simulated_council_tax: 4170.98
+
+- name: England Band H is 2/1 of the Maidstone Band D amount
+  period: 2026
+  absolute_error_margin: 0.01
+  input:
+    people:
+      person:
+        age: 40
+    benunits:
+      benunit:
+        members: [person]
+    households:
+      household:
+        members: [person]
+        region: SOUTH_EAST
+        local_authority: MAIDSTONE
+        council_tax_band: H
+  output:
+    council_tax_band_d_amount: 2502.59
+    simulated_council_tax: 5005.18
+
+- name: Wales Band I (the ninth, Wales-only band) is 21/9 of Band D
+  period: 2026
+  absolute_error_margin: 0.01
+  input:
+    people:
+      person:
+        age: 40
+    benunits:
+      benunit:
+        members: [person]
+    households:
+      household:
+        members: [person]
+        region: WALES
+        local_authority: CARDIFF
+        council_tax_band: I
+  output:
+    council_tax_band_d_amount: 2013.18
+    simulated_council_tax: 4697.42
+
+- name: "Band D identity: liability equals the Band D amount in Cardiff"
+  period: 2026
+  absolute_error_margin: 0.01
+  input:
+    people:
+      person:
+        age: 40
+    benunits:
+      benunit:
+        members: [person]
+    households:
+      household:
+        members: [person]
+        region: WALES
+        local_authority: CARDIFF
+        council_tax_band: D
+  output:
+    council_tax_band_d_amount: 2013.18
+    simulated_council_tax: 2013.18
+
+- name: Scotland Band H uses the 882/360 multiplier from April 2017
+  period: 2026
+  absolute_error_margin: 0.01
+  input:
+    people:
+      person:
+        age: 40
+    benunits:
+      benunit:
+        members: [person]
+    households:
+      household:
+        members: [person]
+        region: SCOTLAND
+        local_authority: CITY_OF_EDINBURGH
+        council_tax_band: H
+  output:
+    council_tax_band_d_amount: 1626.05
+    simulated_council_tax: 3983.82
+
+- name: "Band D identity: liability equals the Band D amount in Maidstone"
+  period: 2026
+  absolute_error_margin: 0.01
+  input:
+    people:
+      person:
+        age: 40
+    benunits:
+      benunit:
+        members: [person]
+    households:
+      household:
+        members: [person]
+        region: SOUTH_EAST
+        local_authority: MAIDSTONE
+        council_tax_band: D
+  output:
+    council_tax_band_d_amount: 2502.59
+    simulated_council_tax: 2502.59
+
+- name: "Fiscal 2025 carries its own Band D level in England (not the 2026-27 one)"
+  period: 2025
+  absolute_error_margin: 0.01
+  input:
+    people:
+      person:
+        age: 40
+    benunits:
+      benunit:
+        members: [person]
+    households:
+      household:
+        members: [person]
+        region: SOUTH_EAST
+        local_authority: MAIDSTONE
+        council_tax_band: D
+  output:
+    council_tax_band_d_amount: 2403.78
+    simulated_council_tax: 2403.78
+
+- name: "Fiscal 2025 carries its own Band D level in Wales"
+  period: 2025
+  absolute_error_margin: 0.01
+  input:
+    people:
+      person:
+        age: 40
+    benunits:
+      benunit:
+        members: [person]
+    households:
+      household:
+        members: [person]
+        region: WALES
+        local_authority: CARDIFF
+        council_tax_band: D
+  output:
+    council_tax_band_d_amount: 1926.18
+    simulated_council_tax: 1926.18
+
+- name: "Scotland Band H at 2025 uses the 2025-26 Band D level"
+  period: 2025
+  absolute_error_margin: 0.01
+  input:
+    people:
+      person:
+        age: 40
+    benunits:
+      benunit:
+        members: [person]
+    households:
+      household:
+        members: [person]
+        region: SCOTLAND
+        local_authority: CITY_OF_EDINBURGH
+        council_tax_band: H
+  output:
+    council_tax_band_d_amount: 1563.51
+    simulated_council_tax: 3830.60
+
+- name: "Scotland Band H before April 2017 used the original 18/9 proportion"
+  period: 2016
+  absolute_error_margin: 0.01
+  input:
+    people:
+      person:
+        age: 40
+    benunits:
+      benunit:
+        members: [person]
+    households:
+      household:
+        members: [person]
+        region: SCOTLAND
+        local_authority: CITY_OF_EDINBURGH
+        council_tax_band: H
+  output:
+    council_tax_band_d_amount: 1563.51
+    simulated_council_tax: 3127.02
+
+- name: "A 2023 unitary authority resolves to its own Band D amount"
+  period: 2026
+  absolute_error_margin: 0.01
+  input:
+    people:
+      person:
+        age: 40
+    benunits:
+      benunit:
+        members: [person]
+    households:
+      household:
+        members: [person]
+        region: SOUTH_WEST
+        local_authority: SOMERSET
+        council_tax_band: D
+  output:
+    council_tax_band_d_amount: 2560.59
+    simulated_council_tax: 2560.59
+
+- name: "Westmorland and Furness, a 2023 unitary, loads at 2025"
+  period: 2025
+  absolute_error_margin: 0.01
+  input:
+    people:
+      person:
+        age: 40
+    benunits:
+      benunit:
+        members: [person]
+    households:
+      household:
+        members: [person]
+        region: NORTH_WEST
+        local_authority: WESTMORLAND_AND_FURNESS
+        council_tax_band: D
+  output:
+    council_tax_band_d_amount: 2389.00
+    simulated_council_tax: 2389.00
+
+- name: "North Yorkshire, a 2023 unitary, resolves to its own Band D amount"
+  period: 2026
+  absolute_error_margin: 0.01
+  input:
+    people:
+      person:
+        age: 40
+    benunits:
+      benunit:
+        members: [person]
+    households:
+      household:
+        members: [person]
+        region: YORKSHIRE
+        local_authority: NORTH_YORKSHIRE
+        council_tax_band: D
+  output:
+    council_tax_band_d_amount: 2544.34
+    simulated_council_tax: 2544.34
+
+- name: "Northern Ireland levies domestic rates, so there is no Band D amount or council tax"
+  period: 2026
+  absolute_error_margin: 0.01
+  input:
+    people:
+      person:
+        age: 40
+    benunits:
+      benunit:
+        members: [person]
+    households:
+      household:
+        members: [person]
+        region: NORTHERN_IRELAND
+        local_authority: BELFAST
+        council_tax_band: D
+  output:
+    council_tax_band_d_amount: 0
+    simulated_council_tax: 0
+
+- name: "A district abolished in April 2023 (Allerdale) has no Band D amount"
+  period: 2026
+  absolute_error_margin: 0.01
+  input:
+    people:
+      person:
+        age: 40
+    benunits:
+      benunit:
+        members: [person]
+    households:
+      household:
+        members: [person]
+        region: NORTH_WEST
+        local_authority: ALLERDALE
+        council_tax_band: D
+  output:
+    council_tax_band_d_amount: 0
+    simulated_council_tax: 0
+
+- name: "With no local authority supplied, the household takes the enum default, Maidstone"
+  period: 2026
+  absolute_error_margin: 0.01
+  input:
+    people:
+      person:
+        age: 40
+    benunits:
+      benunit:
+        members: [person]
+    households:
+      household:
+        members: [person]
+        region: SOUTH_EAST
+        council_tax_band: D
+  output:
+    council_tax_band_d_amount: 2502.59
+    simulated_council_tax: 2502.59
diff --git a/policyengine_uk/tests/test_dated_reform_routes.py b/policyengine_uk/tests/test_dated_reform_routes.py
index 21bdd923ec..7bfffd350d 100644
--- a/policyengine_uk/tests/test_dated_reform_routes.py
+++ b/policyengine_uk/tests/test_dated_reform_routes.py
@@ -1927,12 +1927,27 @@ def restatements(draw):
     stop = start + datetime.timedelta(
         days=draw(st.integers(0, (ends - start).days - 1))
     )
-    route = draw(st.sampled_from(sorted(ROUTES)))
+    # Scenario.parameter_changes types its values as numbers and booleans, so
+    # a list-valued parameter (such as the Universal Credit capital sources)
+    # is restated through the other routes only.
+    routes = sorted(ROUTES)
+    if not isinstance(value, (int, float, bool)):
+        routes.remove("parameter_changes")
+    route = draw(st.sampled_from(routes))
     return name, start, stop, value, route
 
 
 @PROPERTY_SETTINGS
 @given(change=restatements())
+@example(
+    change=(
+        "gov.dwp.universal_credit.means_test.capital.person_sources",
+        datetime.date(2013, 4, 29),
+        datetime.date(2013, 4, 29),
+        [],
+        "reform_dict",
+    )
+)
 def test_restating_a_parameters_own_value_changes_nothing(change):
     name, start, stop, value, route = change
     simulation = ROUTES[route](as_dict(name, start, stop, value))
diff --git a/policyengine_uk/variables/gov/local_authorities/council_tax/council_tax_band_d_amount.py b/policyengine_uk/variables/gov/local_authorities/council_tax/council_tax_band_d_amount.py
new file mode 100644
index 0000000000..fbb11f0f46
--- /dev/null
+++ b/policyengine_uk/variables/gov/local_authorities/council_tax/council_tax_band_d_amount.py
@@ -0,0 +1,41 @@
+from policyengine_uk.model_api import *
+
+
+class council_tax_band_d_amount(Variable):
+    value_type = float
+    entity = Household
+    label = "Band D council tax amount"
+    documentation = (
+        "The Band D council tax amount set by the household's local authority, "
+        "before discounts, exemptions or Council Tax Reduction. For England "
+        "and Wales this is the area figure, which includes the county, police, "
+        "fire, combined authority and parish or community council precepts as "
+        "well as the billing authority's own charge; for Scotland it excludes "
+        "the separately billed water and waste water charges. Fiscal 2025 and "
+        "2026 are loaded for all three nations, so earlier years are held flat "
+        "backwards from 2025.\n\n"
+        "Authority context: the amount is looked up from the household's "
+        "local_authority input, which the dataset must supply. Without it the "
+        "household takes the enum default (Maidstone), so a dataset that does "
+        "not populate local_authority charges every household Maidstone's "
+        "level. Microcosm UK assigns an authority to every household; the "
+        "Enhanced FRS does not, and reweights a national sample per authority "
+        "instead. Northern Ireland districts (domestic rates) and English "
+        "districts abolished in April 2023 have no Band D amount and return "
+        "zero. Downstream calibration should not consume this variable as a "
+        "national total until the dataset supplies local_authority; "
+        "policyengine-uk-data's Band D level target needs "
+        "PolicyEngine/policyengine-uk-data#484 (issue #483) first."
+    )
+    definition_period = YEAR
+    unit = GBP
+    quantity_type = FLOW
+
+    def formula(household, period, parameters):
+        la = household("local_authority", period).decode_to_str()
+        amounts = parameters(period).gov.local_authorities.council_tax.band_d.amounts
+        # Dict lookup rather than bracket indexing: the LocalAuthority enum
+        # also carries Northern Ireland districts (domestic rates, not council
+        # tax) and historical pre-2023 English districts, neither of which has
+        # a Band D amount, so those should return zero rather than raise.
+        return np.array([amounts._children.get(a, 0) for a in la], dtype=float)
diff --git a/policyengine_uk/variables/gov/local_authorities/council_tax/simulated_council_tax.py b/policyengine_uk/variables/gov/local_authorities/council_tax/simulated_council_tax.py
new file mode 100644
index 0000000000..9a3996f543
--- /dev/null
+++ b/policyengine_uk/variables/gov/local_authorities/council_tax/simulated_council_tax.py
@@ -0,0 +1,34 @@
+from policyengine_uk.model_api import *
+
+
+class simulated_council_tax(Variable):
+    value_type = float
+    entity = Household
+    label = "Simulated gross council tax"
+    documentation = (
+        "Gross annual council tax liability computed as the local authority's "
+        "Band D amount multiplied by the statutory band ratio. Before "
+        "discounts, exemptions, premiums and Council Tax Reduction."
+    )
+    definition_period = YEAR
+    unit = GBP
+    quantity_type = FLOW
+
+    def formula(household, period, parameters):
+        band_d = household("council_tax_band_d_amount", period)
+        band = household("council_tax_band", period).decode_to_str()
+        country = household("country", period).decode_to_str()
+        ratios = parameters(period).gov.local_authorities.council_tax.band_ratios
+
+        ratio = np.ones_like(band_d, dtype=float)
+        for key, node in (
+            ("ENGLAND", ratios.england),
+            ("WALES", ratios.wales),
+            ("SCOTLAND", ratios.scotland),
+        ):
+            table = node._children
+            values = np.array([float(table.get(b, 1)) for b in band], dtype=float)
+            ratio = np.where(country == key, values, ratio)
+
+        # Northern Ireland uses domestic rates, not council tax.
+        return np.where(country == "NORTHERN_IRELAND", 0, band_d * ratio)