Fix Scottish top rate threshold to use correct above-PA value #1488
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The Scottish top rate (48%) threshold was incorrectly stored as £125,140 (the total income threshold) instead of £112,570 (the amount above personal allowance). PolicyEngine stores income tax thresholds as amounts ABOVE the personal allowance (£12,570), not as total income. The correct calculation is: - Total income threshold: £125,140 - Above PA: £125,140 - £12,570 = £112,570 This bug caused the top rate to effectively start at £137,710 total income instead of £125,140, significantly underestimating the number of top rate taxpayers and the revenue from threshold freezes. Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>
Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>
- Add Scottish Fiscal Commission January 2026 reference to rates.yaml - Add two unit tests for Scottish top rate threshold verification - Remove currency symbols from changelog entry for consistency Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>
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Summary
Details
PolicyEngine stores income tax thresholds as amounts above the personal allowance (£12,570), not as total income. The Scottish top rate threshold was incorrectly set to:
The correct calculation:
Impact
This bug caused:
Test plan
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