feat: add Scottish Budget 2026-27 tax and benefit changes #1475
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Implements the Scottish Budget 2026-27 reforms announced by Finance Secretary Shona Robison on 13 January 2026: ## Income Tax Threshold Uplift (7.4% increase) - Basic rate threshold: £16,537 total (£3,967 above PA) - Intermediate rate threshold: £29,526 total (£16,956 above PA) - Higher, Advanced, and Top rate thresholds remain frozen ## SCP Premium for Under-Ones (£40/week) - Children under 1 receive £40/week total (vs £27.15 standard rate) - This is a FIXED total amount, not a bonus on top of standard SCP - Controlled by gov.contrib.scotland.scottish_child_payment.in_effect - Amount now parametric via premium_under_one_amount.yaml These changes take effect from 6 April 2026 (2026-04-06). References: - https://www.gov.scot/publications/scottish-budget-2026-2027/ - https://www.gov.scot/publications/scottish-income-tax-technical-factsheet/ Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>
Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>
Remove the contrib/scotland/scottish_child_payment parameters and reforms since the Scottish Budget 2026-27 policy is now enacted. Changes: - Add premium_under_one_amount parameter with £40/week from 2026-04-06 - Update scottish_child_payment variable to use main parameter directly - Delete contrib parameters (baby_bonus.yaml, in_effect.yaml) - Delete scotland reforms directory - Remove scottish_child_payment_reform from reforms.py - Rewrite tests to verify 2025 (standard rate) vs 2026 (premium rate) Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>
Tests verify: - Basic rate threshold at £3,967 above PA (£16,537 total) - Intermediate rate threshold at £16,956 above PA (£29,526 total) - Threshold uplift effect (2025 vs 2026 comparison) - English taxpayers unaffected by Scottish thresholds Source: Scottish Income Tax 2026-27 Technical Factsheet, Table 1 https://www.gov.scot/publications/scottish-income-tax-technical-factsheet/ Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>
Per Scottish Budget 2026-27: - SCP inflation increase to £28.20/week from April 2026 - Baby boost (£40/week for under-1s) "will be paid in 2027-28" Source: https://www.gov.scot/publications/scottish-budget-2026-2027/pages/6/ Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>
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- Remove unconfirmed 2026 rate (£28.20) - belongs in PR #1475 - Update baby bonus tests to use £27.15 standard rate - Baby boost starts 2027-04-06 per Scottish Budget announcement Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>
- 2026: £28.20/week standard rate (no baby boost) - 2027: £40/week for babies, £28.20/week for older children Per Scottish Budget: baby boost "will be paid in 2027-28" Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>
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Baby bonus (SCP Premium for under-ones) belongs in draft PR #1475 (Scottish Budget 2026-27), not this deterministic takeup PR. This PR is only about migrating from random() to would_claim_scp. Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>
MaxGhenis
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* Remove randomness from country package Move stochastic variable generation to data package. Variables now read pre-computed values from datasets for deterministic, reproducible calculations. Changes: - would_claim_pc, would_claim_uc, would_claim_child_benefit, child_benefit_opts_out, would_evade_tv_licence_fee, household_owns_tv, main_residential_property_purchased_is_first_home, is_disabled_for_benefits: Remove formulas, use default_value - would_claim_marriage_allowance: New variable for take-up decision - marriage_allowance: Use would_claim_marriage_allowance instead of random() - attends_private_school: Use pre-generated random draw from dataset - is_higher_earner: Use age as deterministic tie-breaker instead of random() 🤖 Generated with [Claude Code](https://claude.com/claude-code) Co-Authored-By: Claude <noreply@anthropic.com> * Add tests for deterministic stochastic variables Tests verify: - Default values work correctly in policy calculator mode - Variables can be explicitly overridden in situations - is_higher_earner uses deterministic tie-breaking (older wins) - Calculations are deterministic across multiple runs 🤖 Generated with [Claude Code](https://claude.com/claude-code) Co-Authored-By: Claude <noreply@anthropic.com> * Format test file with black * Add Scottish Child Payment with deterministic take-up Add SCP variable and parameters with would_claim_scp for deterministic take-up (matching the pattern for other benefits in this PR). Changes: - Add would_claim_scp variable (default True, generated in dataset) - Add scottish_child_payment variable with defined_for="would_claim_scp" - Add is_scp_eligible_child helper variable - Add SCP parameters with legislation references: - amount.yaml (Regulation 20) - max_age.yaml (Regulation 18) - premium_under_one_amount.yaml (Scottish Budget 2026-27) - qualifying_benefits/ (Regulation 14) - takeup_rate/ (for dataset generation) - Add tests for SCP baby bonus Source: The Scottish Child Payment Regulations 2020 https://www.legislation.gov.uk/ssi/2020/351/contents Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com> * Refactor SCP to Person level with adds=['benunit'] * Add is_scp_eligible Person variable, simplify scottish_child_payment * Split SCP into Person and BenUnit variables - Create scottish_child_payment_person at Person level with defined_for - Keep scottish_child_payment at BenUnit level using adds to aggregate - Maintains backward compatibility with existing tests Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com> * Fix SCP parameters: add 2026 rate, correct baby boost start date - Add 2026-04-01: £28.20 rate (inflation increase per Scottish Budget) - Change baby boost start from 2026-04-06 to 2027-04-06 (payments start 2027-28) Source: Scottish Budget 2026-27 confirms "will be paid in 2027-28" https://www.gov.scot/publications/scottish-budget-2026-2027/pages/6/ Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com> * Fix SCP tests: use confirmed rate, baby boost starts 2027 - Remove unconfirmed 2026 rate (£28.20) - belongs in PR #1475 - Update baby bonus tests to use £27.15 standard rate - Baby boost starts 2027-04-06 per Scottish Budget announcement Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com> * Remove baby bonus from takeup migration PR Baby bonus (SCP Premium for under-ones) belongs in draft PR #1475 (Scottish Budget 2026-27), not this deterministic takeup PR. This PR is only about migrating from random() to would_claim_scp. Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com> * Simplify SCP to Person level directly Remove BenUnit wrapper - scottish_child_payment is now Person-level with defined_for="is_scp_eligible". Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com> * Update SCP tests for Person-level output format Tests now specify per-person expected values since scottish_child_payment is a Person-level variable. Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com> --------- Co-authored-by: Claude <noreply@anthropic.com>
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Summary
Implements the Scottish Budget 2026-27 reforms announced by Finance Secretary Shona Robison on 13 January 2026. This is a draft PR to be merged when the budget becomes law.
Changes
Income Tax Threshold Uplift (7.4% increase)
From the Scottish Income Tax Technical Factsheet:
SCP Inflation Increase (£28.20/week from April 2026)
SCP Premium for Under-Ones (£40/week from April 2027)
Implementation Details
Income Tax
parameters/gov/hmrc/income_tax/rates/scotland/rates.yamlwith 2026-04-06 threshold valuesSCP
2026-04-01: 28.20toamount.yaml(inflation increase)premium_under_one_amount.yamlto £40/week starting 2027-04-06References
Note
This draft PR should be merged once the Scottish Budget 2026-27 is passed into law.
🤖 Generated with Claude Code