diff --git a/changelog_entry.yaml b/changelog_entry.yaml
index e69de29bb..fde4a452d 100644
--- a/changelog_entry.yaml
+++ b/changelog_entry.yaml
@@ -0,0 +1,7 @@
+- bump: minor
+  changes:
+    added:
+    - ONS household population data from 2001-2043.
+    - Council tax per household projections from OBR data.
+    changed:
+    - Updated employer National Insurance contribution rate to 15% from April 6, 2025.
diff --git a/policyengine_uk/parameters/gov/obr/council_tax.yaml b/policyengine_uk/parameters/gov/obr/council_tax.yaml
index b5cb424ee..996f61e67 100644
--- a/policyengine_uk/parameters/gov/obr/council_tax.yaml
+++ b/policyengine_uk/parameters/gov/obr/council_tax.yaml
@@ -1,15 +1,18 @@
-description: OBR forecast for council tax.
+description: OBR forecast for council tax per household.
 values:
-  2023-01-01: 44.5
-  2024-01-01: 47.7
-  2025-01-01: 50.2
-  2026-01-01: 52.8
-  2027-01-01: 55.6
-  2028-01-01: 58.5
-  2029-01-01: 61.5
+  2023-01-01: 1_851.4  # 44.5bn / 24.041m households = £1,851 per household
+  2024-01-01: 1_970.1  # 47.7bn / 24.209m households = £1,970 per household
+  2025-01-01: 2_060.1  # 50.2bn / 24.367m households = £2,060 per household
+  2026-01-01: 2_152.7  # 52.8bn / 24.525m households = £2,153 per household
+  2027-01-01: 2_252.9  # 55.6bn / 24.686m households = £2,253 per household
+  2028-01-01: 2_354.3  # 58.5bn / 24.844m households = £2,354 per household
+  2029-01-01: 2_460.4  # 61.5bn / 24.998m households = £2,460 per household
 metadata:
   label: Council tax uprating
   reference:
     - title: OBR March 2025 EFO
       href: https://obr.uk/efo/economic-and-fiscal-outlook-march-2025/
-      # Table A.5: Current receipt
\ No newline at end of file
+  # Calculations based on:
+  # - Council tax receipts from OBR March 2025 EFO, Table A.5: Current receipts (£bn)
+  # - Household population data from ons.household.yaml
+  # - Per household = Total receipts (£bn) / Number of households (millions) × 1000
\ No newline at end of file
diff --git a/policyengine_uk/parameters/gov/ons/household.yaml b/policyengine_uk/parameters/gov/ons/household.yaml
new file mode 100644
index 000000000..dd7a1f607
--- /dev/null
+++ b/policyengine_uk/parameters/gov/ons/household.yaml
@@ -0,0 +1,51 @@
+description: Number of households in the UK.
+values:
+  2001-01-01: 20_451_000
+  2002-01-01: 20_553_000
+  2003-01-01: 20_651_000
+  2004-01-01: 20_752_000
+  2005-01-01: 20_926_000
+  2006-01-01: 21_072_000
+  2007-01-01: 21_223_000
+  2008-01-01: 21_400_000
+  2009-01-01: 21_562_000
+  2010-01-01: 21_743_000
+  2011-01-01: 21_976_000
+  2012-01-01: 22_130_000
+  2013-01-01: 22_291_000
+  2014-01-01: 22_488_000
+  2015-01-01: 22_681_000
+  2016-01-01: 22_884_000
+  2017-01-01: 23_047_000
+  2018-01-01: 23_204_000
+  # Projections:
+  2019-01-01: 23_385_000
+  2020-01-01: 23_543_000
+  2021-01-01: 23_689_000
+  2022-01-01: 23_868_000
+  2023-01-01: 24_041_000
+  2024-01-01: 24_209_000
+  2025-01-01: 24_367_000
+  2026-01-01: 24_525_000
+  2027-01-01: 24_686_000
+  2028-01-01: 24_844_000
+  2029-01-01: 24_998_000
+  2030-01-01: 25_147_000
+  2031-01-01: 25_299_000
+  2032-01-01: 25_451_000
+  2033-01-01: 25_601_000
+  2034-01-01: 25_746_000
+  2035-01-01: 25_889_000
+  2036-01-01: 26_034_000
+  2037-01-01: 26_175_000
+  2038-01-01: 26_313_000
+  2039-01-01: 26_444_000
+  2040-01-01: 26_573_000
+  2041-01-01: 26_705_000
+  2042-01-01: 26_834_000
+  2043-01-01: 26_953_000
+metadata:
+  unit: household
+  reference:
+    - title: National population projections (2018-based) | ONS | Figure 1
+      href: https://www.ons.gov.uk/peoplepopulationandcommunity/populationandmigration/populationprojections/bulletins/householdprojectionsforengland/2018based
\ No newline at end of file