MaxGhenis · Oct 11, 2026 · Oct 11, 2026 · Oct 11, 2026 · Oct 11, 2026 · Oct 11, 2026
diff --git a/.gitignore b/.gitignore
@@ -57,6 +57,7 @@ policyengine_uk/calibration/*.h5
 !uprating_growth_factors.csv
 !policyengine_uk/parameters/gov/dwp/LHA/lha_published_rates_sources.csv
 !policyengine_uk/tests/fixtures/energy_prices/*.csv
+!policyengine_uk/tests/fixtures/sdlt_ltt_main_grid_2018_2030.csv
 
 # Virtual environments
 .venv/

diff --git a/changelog.d/2090.fixed.md b/changelog.d/2090.fixed.md
@@ -0,0 +1 @@
+The model now deducts from Council Tax Reduction income only the income tax and National Insurance each scheme allows: in Scotland's working-age scheme the extra tax earnings cause and the notional tax on self-employed profit, and in the pensioner schemes of England, Wales and Scotland that same earnings tax, the tax on the other counted income and the notional tax on profit, with no tax on savings, dividends, rent from property or the Scottish Carer Supplement, and no High Income Child Benefit Charge, where earnings do not raise them.
diff --git a/changelog.d/2106.fixed.md b/changelog.d/2106.fixed.md
@@ -0,0 +1 @@
+The model now sets the Personal Allowance, other allowances and trade loss relief against non-savings, savings and dividend income in the way that gives the least tax (ITA 2007 s. 25(2)), and from 2027-28 against other income before property, savings and dividend income (s. 25(3A)), where it previously always took them from non-savings income first. Pension relief stays on non-savings income, and the income tax that Universal Credit deducts from earnings still follows the order non-savings, savings, dividends.
diff --git a/changelog.d/2120.fixed.md b/changelog.d/2120.fixed.md
@@ -0,0 +1 @@
+The model now counts a carer's Universal Credit award with the carer element, where the award comes to at least one penny, when deciding the severe disability premium and the Pension Credit severe disability addition, and in Scotland's working-age council tax reduction it counts such an award for the carer premium from 1 April 2022 (#2120, #2124).
diff --git a/changelog.d/2310.fixed.md b/changelog.d/2310.fixed.md
@@ -0,0 +1 @@
+Pay Carer's Allowance and Carer Support Payment, and count a carer for the Universal Credit carer element, on caring hours only where the new input `cares_for_severely_disabled_person` says the person cared for gets a qualifying disability benefit; it defaults to true, so results change only where a calculation sets it false.
diff --git a/changelog.d/2565.fixed.md b/changelog.d/2565.fixed.md
@@ -0,0 +1 @@
+The model no longer pays income-related ESA to a claimant who has reached pensionable age, or to a couple that would get State Pension Credit without that award, whether the model's formulas, an input or a reform set that Pension Credit, and it pays no Pension Credit to a couple while it pays the couple income-related ESA (Welfare Reform Act 2007 s.1(3)(c) and Sch 1 para 6(1)(c) and (d)).
diff --git a/changelog.d/2633.added.md b/changelog.d/2633.added.md
@@ -0,0 +1 @@
+Added property tests for VAT grossing (the routing between the survey coverage and the deprecated combined factor, including the closeness band, and VAT as the statutory liability over the shipped product, times one minus private school fees' share of VAT receipts, on a vector of households), a test that the model grosses 2024 by the same product as later years, and a record of how the coverage of 0.67 performed on the Microcosm UK cuts `6cba5d71` and `a133f37a`, which followed `f9d1922c` (#2633).
diff --git a/changelog.d/2633.changed.md b/changelog.d/2633.changed.md
@@ -0,0 +1 @@
+Re-derived the survey VAT consumption coverage (`gov.simulation.vat.survey_consumption_coverage`) on the certified Microcosm UK 2024-25 national cut `a6299504` and moved it from 0.67 to 0.69: on that cut, 2024-25 total `vat` comes to £176.06bn at 0.67, 3.0% above OBR receipts of £170.994bn, and £171.02bn at 0.69, 0.02% above. Moved the deprecated combined factor `gov.simulation.microdata_vat_coverage` to the new product, 0.483.
diff --git a/changelog.d/2773.fixed.md b/changelog.d/2773.fixed.md
@@ -0,0 +1 @@
+The aggregate checker reports non-finite baseline values as blocking failures and continues checking readable households.
diff --git a/changelog.d/2791.fixed.md b/changelog.d/2791.fixed.md
@@ -0,0 +1 @@
+Pay the Scottish Carer Supplement for each award week in which Carer Support Payment is payable, up to 52 a year, counting the weeks from the larger of the payment and the entitlement before the overlapping-benefit reduction, so a carer paid 13 weeks of Carer Support Payment after moving to England gets £152.10 of supplement in 2026-27 rather than £608.40.
diff --git a/changelog.d/2801.fixed.md b/changelog.d/2801.fixed.md
@@ -0,0 +1 @@
+The model now dates the main residential rates in s. 55(1B) Table A from 4 December 2014, first-time buyers' relief from 22 November 2017, the higher rates for additional dwellings from 1 April 2016 and the 2016 non-residential rates from 17 March 2016. Before 17 March 2016 it computes SDLT on a non-residential purchase as one percentage of the whole price. It computes SDLT on purchases in Wales until 31 March 2018 and Land Transaction Tax from 1 April 2018.
diff --git a/changelog.d/2863.fixed.md b/changelog.d/2863.fixed.md
@@ -0,0 +1 @@
+The student loan repayment formula now charges Plan 5 borrowers nothing before 6 April 2026, as SI 2009/470 reg. 15(2BA) requires.
diff --git a/changelog.d/2874.changed.md b/changelog.d/2874.changed.md
@@ -0,0 +1 @@
+The test suite fails on any new random draw, sampling call or hash of entity ids in the package, and lists today's draws in a ratchet.
diff --git a/changelog.d/2875.fixed.md b/changelog.d/2875.fixed.md
@@ -0,0 +1 @@
+The real income variables now price to the year in gov.simulation.price_base_year (2026) instead of the year the simulation runs, and inflation_adjustment_ahc uses one price index on both sides of its ratio.
diff --git a/changelog.d/cb-qyp-school-leaver-routes.fixed.md b/changelog.d/cb-qyp-school-leaver-routes.fixed.md
@@ -0,0 +1 @@
+Added the Child Benefit qualifying young person conditions for young people who have left education (Child Benefit (General) Regulations 2006 regs 4, 5 and 7), which the Housing Benefit, legacy benefit and Council Tax Reduction young persons follow: a 16-year-old counts until the 31 August after their 16th birthday, in any year that starts before it, two new inputs place the 20-week extension period and the terminal date, and the model pays no Child Benefit for a young person who qualifies only through the terminal date and works 24 hours or more a week (reg. 7(3)). A young person who reports their own Universal Credit, Employment and Support Allowance or income-based Jobseeker's Allowance, or their own Income Support while DWP pays it, is not one, on any route (reg. 8).
diff --git a/changelog.d/ctc-qyp-school-leaver-routes.fixed.md b/changelog.d/ctc-qyp-school-leaver-routes.fixed.md
@@ -0,0 +1 @@
+Counted a 16-year-old who has left education as a Child Tax Credit qualifying young person until the 31 August after their 16th birthday, in any year that starts before it (Child Tax Credit Regulations 2002 reg. 4), and added an input for the 20 weeks after leaving while registered for work or training (reg. 5(3)(b)). Remunerative work of 24 hours a week ends both for a young person who has left education (reg. 5(4)(a)), and Income Support received by the young person ends every route (reg. 5(4)(c)).
diff --git a/changelog.d/qyp-income-support-exclusion.fixed.md b/changelog.d/qyp-income-support-exclusion.fixed.md
@@ -0,0 +1 @@
+Tested that Pension Credit, Child Benefit and Child Tax Credit each stop counting a young person who receives Income Support in their own right as a qualifying young person, and Universal Credit does not (SPC Regs 2002 reg. 4A(5); Child Benefit (General) Regulations 2006 reg. 8(2)(a); CTC Regs 2002 reg. 5(4)(c); UC Regs 2013 reg. 5(5)), in the baseline and under reforms that remove Income Support. Pension Credit and Child Tax Credit read the benefit unit's calculated Income Support for whichever of the claimant and partner receives it, so a reform that pays no Income Support ends the exclusion for that person; Child Benefit reads the young person's own report while Income Support is in payment.
diff --git a/changelog.d/qyp-terminal-date-19.fixed.md b/changelog.d/qyp-terminal-date-19.fixed.md
@@ -0,0 +1 @@
+Placed the 1 September following a qualifying young person's 19th birthday from their date of birth, for Universal Credit and Pension Credit (UC Regs 2013 reg. 5(1)(b); SPC Regs 2002 reg. 4A(1)(b)). The model now counts a 19-year-old in education for Universal Credit by default in household calculations, as the microdata already did, and applies the date to Pension Credit, which had no terminal date.
diff --git a/changelog.d/state-pension-reported-weeks.changed.md b/changelog.d/state-pension-reported-weeks.changed.md
@@ -0,0 +1 @@
+Document that state_pension_reported is the weekly State Pension times 52, the weeks the State Pension components read it back at, and test the route from a survey's weekly amount to Income Tax under the Pension Tax Allowance.
diff --git a/docs/book/assumptions/mp30k-uk-switch-plan.md b/docs/book/assumptions/mp30k-uk-switch-plan.md
@@ -115,14 +115,13 @@ A documented gate must pass before any environment's default changes:
 
 1. Dataset choice stays a runtime setting: no code in this repo branches on
    which dataset is loaded. One parameter is tied to the dataset, though:
-   `gov.simulation.vat.survey_consumption_coverage` is calibrated to one
-   Microcosm UK 2024-25 national cut only
-   (`microcosm-uk-2024-25-national-20261002T230158Z-5c6b3f68`; policyengine.py
-   6.10.0 pins the later cut
-   `microcosm-uk-2024-25-national-20261019T083323Z-6cba5d71`), puts 2024-25
-   VAT 38% (policyengine-uk-data 1.56.16) or 44% (1.58.0) above receipts on
-   the Enhanced FRS 2024-25, and has to be re-derived when the dataset it
-   should match changes (`docs/engineering/vat-coverage.md`).
+   `gov.simulation.vat.survey_consumption_coverage` matches 2024-25 receipts
+   on one Microcosm UK 2024-25 national cut only
+   (`microcosm-uk-2024-25-national-20261025T091414Z-a6299504`, which
+   policyengine.py 6.11.1 and 6.12.0 certify), and puts 2024-25 VAT 38% above
+   receipts on the Enhanced FRS 2024-25 (policyengine-uk-data 1.58.1).
+   Re-derive it, with `docs/engineering/vat-coverage.md`, whenever the dataset
+   it should match changes.
 2. While both are in use, CI runs the dataset-dependent tests on both.
 3. The default is set per environment: for direct use of this package
    through `POLICYENGINE_UK_DEFAULT_DATASET`; for this repository's tests

diff --git a/docs/book/programs/gov/dwp/disability-legacy-benefits.md b/docs/book/programs/gov/dwp/disability-legacy-benefits.md
@@ -94,7 +94,8 @@ annual netting does not represent benefit spells at different weekly rates.
 The focused household tests retain live UC eligibility, disability/carer
 elements and final awards. Legacy receipt and disability-assessment inputs are
 assumptions, not a re-derivation of IB/SDA entitlement. The care-hours interface
-does not identify the person cared for or check their qualifying benefit. No
+does not identify the person cared for, and reads their qualifying benefit only
+from the input `cares_for_severely_disabled_person`, which defaults to true. No
 private-data impact or Axiom parity has been measured.
 
 ## References

diff --git a/docs/book/programs/gov/hmrc/stamp-duty.ipynb b/docs/book/programs/gov/hmrc/stamp-duty.ipynb
@@ -16,6 +16,22 @@
     "The regulation of SDLT is defined in part 4 of the [Finance Act 2003](https://www.legislation.gov.uk/ukpga/2003/14/part/4)."
    ]
   },
+  {
+   "attachments": {},
+   "cell_type": "markdown",
+   "metadata": {},
+   "source": [
+    "## Start dates in 2014 to 2018\n",
+    "\n",
+    "This page lists the effective date Parliament set for each change. Each model year reads the parameters in force on 30 April:\n",
+    "\n",
+    "- Parliament started the main residential rates in s55(1B) Table A, charged on slices of the price, on 4 December 2014 ([Stamp Duty Land Tax Act 2015 s2(2)](https://www.legislation.gov.uk/ukpga/2015/1/section/2)). Every model year from 2015 reads them.\n",
+    "- Parliament started first-time buyers' relief on 22 November 2017 ([Finance Act 2018 s41(8)](https://www.legislation.gov.uk/ukpga/2018/3/section/41/enacted)), so the model grants it from model year 2018.\n",
+    "- Parliament started the higher rates for additional dwellings on 1 April 2016 ([Finance Act 2016 s128(5)](https://www.legislation.gov.uk/ukpga/2016/24/section/128/enacted)). In model year 2015 a buyer of an additional dwelling pays the main rates at any price, and a reform to the main rates reaches that buyer too. A reform can move the switch through `gov.hmrc.stamp_duty.residential.purchase.additional.higher_rates_apply`.\n",
+    "- Parliament moved non-residential purchases to sliced rates, and added a 2% band on lease rent above £5 million, from 17 March 2016 ([Finance Act 2016 s127(12)](https://www.legislation.gov.uk/ukpga/2016/24/section/127/enacted)). Before then HMRC charged the whole price of a non-residential purchase at the percentage for its band under [s55(2) Table B as at 30 April 2015](https://www.legislation.gov.uk/ukpga/2003/14/section/55/2015-04-30): 0% up to £150,000, 1% up to £250,000, 3% up to £500,000 and 4% above. The model applies that table in model year 2015, so a £1,000,000 purchase pays £40,000 in model year 2015 and £39,500 from model year 2016.\n",
+    "- HMRC charged SDLT on land in Wales until 31 March 2018 ([Finance Act 2003 s48(1)(a) as at 30 April 2017](https://www.legislation.gov.uk/ukpga/2003/14/section/48/2017-04-30)). Parliament ended that charge from 1 April 2018 ([Wales Act 2014 s16](https://www.legislation.gov.uk/ukpga/2014/29/section/16), on the date the Treasury appointed in [SI 2018/214](https://www.legislation.gov.uk/uksi/2018/214/article/2/made)), and the Welsh Revenue Authority charges Land Transaction Tax from then ([Land Transaction Tax and Anti-avoidance of Devolved Taxes (Wales) Act 2017 s2](https://www.legislation.gov.uk/anaw/2017/1/section/2)). The model computes SDLT on purchases in Wales up to model year 2017 and Land Transaction Tax from model year 2018. A reform can move the switch through `gov.hmrc.stamp_duty.applies_in_wales`."
+   ]
+  },
   {
    "attachments": {},
    "cell_type": "markdown",

diff --git a/docs/book/validation/student-loan-repayments.ipynb b/docs/book/validation/student-loan-repayments.ipynb
@@ -20,7 +20,7 @@
     "- **Plan 1**: loans for courses begun on or before 31 August 2012 under England's and Wales's student support regulations ([SI 2009/470 reg. 3A](https://www.legislation.gov.uk/uksi/2009/470/regulation/3A)), and every Student Finance Northern Ireland loan ([GOV.UK](https://www.gov.uk/repaying-your-student-loan/which-repayment-plan-you-are-on)). 9% of income above £24,990.\n",
     "- **Plan 2**: Student Finance England loans for courses begun from 1 September 2012 to 31 July 2023, and Student Finance Wales loans for courses begun on or after 1 September 2012 ([GOV.UK](https://www.gov.uk/repaying-your-student-loan/which-repayment-plan-you-are-on)). 9% of income above £27,295.\n",
     "- **Plan 4**: loans under Scottish student loan regulations from 1998 onwards whose repayments the Scottish Ministers have HMRC collect ([SI 2009/470 reg. 3D](https://www.legislation.gov.uk/uksi/2009/470/regulation/3D)). GOV.UK puts every Student Awards Agency Scotland loan on Plan 4. 9% of income above £31,395.\n",
-    "- **Plan 5**: Student Finance England loans for courses begun on or after 1 August 2023 ([GOV.UK](https://www.gov.uk/repaying-your-student-loan/which-repayment-plan-you-are-on)). Its threshold is £25,000, but SI 2009/470 reg. 15(2BA), which [SI 2022/1335 reg. 15(9)](https://www.legislation.gov.uk/uksi/2022/1335/regulation/15/made) inserted, requires no repayment of a Plan 5 loan on or before 5 April 2026, so Plan 5 borrowers owe nothing in 2024-25 or 2025-26. The model doesn't yet apply reg. 15(2BA): it charges Plan 5 borrowers 9% of income above £25,000 in those years too.\n",
+    "- **Plan 5**: Student Finance England loans for courses begun on or after 1 August 2023 ([GOV.UK](https://www.gov.uk/repaying-your-student-loan/which-repayment-plan-you-are-on)). Its threshold is £25,000, but SI 2009/470 reg. 15(2BA), which [SI 2022/1335 reg. 15(9)](https://www.legislation.gov.uk/uksi/2022/1335/regulation/15/made) inserted, requires no repayment of a Plan 5 loan on or before 5 April 2026, so Plan 5 borrowers owe nothing in 2024-25 or 2025-26. From 2026-27 they repay 9% of income above that threshold.\n",
     "- **Postgraduate**: 6% of income above £21,000.\n",
     "\n",
     "The FRS captures reported student loan repayments, while PolicyEngine calculates repayments based on income and loan plan type."
@@ -146,17 +146,15 @@
    "source": [
     "## What can make the two measures differ\n",
     "\n",
-    "The code compares two variables. `student_loan_repayments` holds the repayments a dataset reports; where a dataset supplies none, its formula returns `student_loan_repayment`, and the two match exactly. `student_loan_repayment` applies the plan's rate to income above the plan's threshold, and caps the result at `student_loan_balance` where the balance is known. They can differ for these reasons:\n",
+    "The code compares two variables. `student_loan_repayments` holds the repayments a dataset reports; where a dataset supplies none, its formula returns `student_loan_repayment`, and the two match exactly. `student_loan_repayment` applies the plan's rate to income above the plan's threshold, charges a Plan 5 borrower nothing before 2026-27, and caps the result at `student_loan_balance` where the balance is known. They can differ for these reasons:\n",
     "\n",
     "1. **Annual income**: the model applies the threshold to a year's income (`student_loan_income`, net income less benefits in kind), not to each pay period, so it doesn't reflect how income varies within the year.\n",
     "\n",
     "2. **Voluntary repayments**: the formula holds no voluntary repayments, so it leaves out any that a reported figure includes.\n",
     "\n",
     "3. **One plan per person**: `student_loan_plan` gives each person one plan, so the model can't charge someone who holds loans on two plans for both.\n",
     "\n",
-    "4. **Missing plans**: a person with no plan (`NONE`) gets no modelled repayment, whatever they report. [#1764](https://github.com/PolicyEngine/policyengine-uk/issues/1764) reports a run on `enhanced_frs_2023_24.h5` with policyengine-uk 2.88.43 for 2026 in which 5,570 people had a reported repayment and none had a modelled one, because no person had a plan.\n",
-    "\n",
-    "5. **Plan 5 before April 2026**: the model charges Plan 5 borrowers repayments that the law doesn't require until 6 April 2026 (see the plan list above)."
+    "4. **Missing plans**: a person with no plan (`NONE`) gets no modelled repayment, whatever they report. [#1764](https://github.com/PolicyEngine/policyengine-uk/issues/1764) reports a run on `enhanced_frs_2023_24.h5` with policyengine-uk 2.88.43 for 2026 in which 5,570 people had a reported repayment and none had a modelled one, because no person had a plan."
    ]
   },
   {
Original file line number	Diff line number	Diff line change
		@@ -0,0 +1 @@
		The model now deducts from Council Tax Reduction income only the income tax and National Insurance each scheme allows: in Scotland's working-age scheme the extra tax earnings cause and the notional tax on self-employed profit, and in the pensioner schemes of England, Wales and Scotland that same earnings tax, the tax on the other counted income and the notional tax on profit, with no tax on savings, dividends, rent from property or the Scottish Carer Supplement, and no High Income Child Benefit Charge, where earnings do not raise them.
Original file line number	Diff line number	Diff line change
		@@ -0,0 +1 @@
		The model now sets the Personal Allowance, other allowances and trade loss relief against non-savings, savings and dividend income in the way that gives the least tax (ITA 2007 s. 25(2)), and from 2027-28 against other income before property, savings and dividend income (s. 25(3A)), where it previously always took them from non-savings income first. Pension relief stays on non-savings income, and the income tax that Universal Credit deducts from earnings still follows the order non-savings, savings, dividends.
Original file line number	Diff line number	Diff line change
		@@ -0,0 +1 @@
		The model now counts a carer's Universal Credit award with the carer element, where the award comes to at least one penny, when deciding the severe disability premium and the Pension Credit severe disability addition, and in Scotland's working-age council tax reduction it counts such an award for the carer premium from 1 April 2022 (#2120, #2124).
Original file line number	Diff line number	Diff line change
		@@ -0,0 +1 @@
		Pay Carer's Allowance and Carer Support Payment, and count a carer for the Universal Credit carer element, on caring hours only where the new input `cares_for_severely_disabled_person` says the person cared for gets a qualifying disability benefit; it defaults to true, so results change only where a calculation sets it false.
Original file line number	Diff line number	Diff line change
		@@ -0,0 +1 @@
		The model no longer pays income-related ESA to a claimant who has reached pensionable age, or to a couple that would get State Pension Credit without that award, whether the model's formulas, an input or a reform set that Pension Credit, and it pays no Pension Credit to a couple while it pays the couple income-related ESA (Welfare Reform Act 2007 s.1(3)(c) and Sch 1 para 6(1)(c) and (d)).
Original file line number	Diff line number	Diff line change
		@@ -0,0 +1 @@
		Added property tests for VAT grossing (the routing between the survey coverage and the deprecated combined factor, including the closeness band, and VAT as the statutory liability over the shipped product, times one minus private school fees' share of VAT receipts, on a vector of households), a test that the model grosses 2024 by the same product as later years, and a record of how the coverage of 0.67 performed on the Microcosm UK cuts `6cba5d71` and `a133f37a`, which followed `f9d1922c` (#2633).
Original file line number	Diff line number	Diff line change
		@@ -0,0 +1 @@
		Re-derived the survey VAT consumption coverage (`gov.simulation.vat.survey_consumption_coverage`) on the certified Microcosm UK 2024-25 national cut `a6299504` and moved it from 0.67 to 0.69: on that cut, 2024-25 total `vat` comes to £176.06bn at 0.67, 3.0% above OBR receipts of £170.994bn, and £171.02bn at 0.69, 0.02% above. Moved the deprecated combined factor `gov.simulation.microdata_vat_coverage` to the new product, 0.483.
Original file line number	Diff line number	Diff line change
		@@ -0,0 +1 @@
		The aggregate checker reports non-finite baseline values as blocking failures and continues checking readable households.
Original file line number	Diff line number	Diff line change
		@@ -0,0 +1 @@
		Pay the Scottish Carer Supplement for each award week in which Carer Support Payment is payable, up to 52 a year, counting the weeks from the larger of the payment and the entitlement before the overlapping-benefit reduction, so a carer paid 13 weeks of Carer Support Payment after moving to England gets £152.10 of supplement in 2026-27 rather than £608.40.
Original file line number	Diff line number	Diff line change
		@@ -0,0 +1 @@
		The model now dates the main residential rates in s. 55(1B) Table A from 4 December 2014, first-time buyers' relief from 22 November 2017, the higher rates for additional dwellings from 1 April 2016 and the 2016 non-residential rates from 17 March 2016. Before 17 March 2016 it computes SDLT on a non-residential purchase as one percentage of the whole price. It computes SDLT on purchases in Wales until 31 March 2018 and Land Transaction Tax from 1 April 2018.