{
  "generatedAt": "2026-08-08T22:45:38.929Z",
  "taxYearId": "2026-27",
  "definition": "Marginal rates from engine £1 gross bump (calculateUkIncomeTax unrounded delta). Combined = IT + employee NI only. presentationFrom/To follow official band labels (Scottish Higher from £43,663); fromGrossInclusive may be one pound earlier where the £1-bump foreshadows the next band.",
  "niMethodology": {
    "officialAnnualPrimaryThreshold": 12570,
    "officialMonthlyPrimaryThreshold": 1048,
    "modelledAnnualPrimaryThresholdFromMonthly": 12576,
    "officialAnnualUpperEarningsLimit": 50270,
    "officialMonthlyUpperEarningsLimit": 4189,
    "modelledAnnualUpperEarningsLimitFromMonthly": 50268,
    "publicFacingWording": "HMRC’s published annual Upper Earnings Limit remains £50,270. Under Sorvuna’s equal-monthly model, the main-to-higher employee NI transition appears around £50,268. HMRC’s published annual Primary Threshold is £12,570; equal-monthly modelling produces a transition around £12,576."
  },
  "wordingNotes": [
    "62% / 69.5% figures are combined marginal Income Tax and employee NI on additional employment income above £100,000 and through the Personal Allowance taper — not overall/effective rates on the whole £100,000 salary.",
    "Scottish 50% combined band: Higher Rate from £43,663 (Intermediate through £43,662).",
    "HMRC’s published annual Upper Earnings Limit remains £50,270. Under Sorvuna’s equal-monthly model, the main-to-higher employee NI transition appears around £50,268. HMRC’s published annual Primary Threshold is £12,570; equal-monthly modelling produces a transition around £12,576."
  ],
  "segments": [
    {
      "region": "rest_of_uk",
      "fromGrossInclusive": 0,
      "toGrossExclusive": 12570,
      "presentationFromGrossInclusive": 0,
      "presentationToGrossExclusive": 12570,
      "sampleGross": 0,
      "marginalIncomeTax": 0,
      "marginalEmployeeNi": 0,
      "marginalCombined": 0,
      "keepOfNextPound": 1,
      "presentationLabel": "rest_of_uk £0–£12569: ~0% IT + ~0% NI = ~0% combined marginal IT+NI",
      "note": "rest_of_uk £0–£12569: ~0% IT + ~0% NI = ~0% combined marginal IT+NI | engine £1-bump sample from £0 (at £0)"
    },
    {
      "region": "rest_of_uk",
      "fromGrossInclusive": 12570,
      "toGrossExclusive": 12576,
      "presentationFromGrossInclusive": 12570,
      "presentationToGrossExclusive": 12576,
      "sampleGross": 12570,
      "marginalIncomeTax": 0.2,
      "marginalEmployeeNi": 0,
      "marginalCombined": 0.2,
      "keepOfNextPound": 0.8,
      "presentationLabel": "rest_of_uk £12570–£12575: ~20% IT + ~0% NI = ~20% combined marginal IT+NI",
      "note": "rest_of_uk £12570–£12575: ~20% IT + ~0% NI = ~20% combined marginal IT+NI | engine £1-bump sample from £12570 (at £12570)"
    },
    {
      "region": "rest_of_uk",
      "fromGrossInclusive": 12576,
      "toGrossExclusive": 50268,
      "presentationFromGrossInclusive": 12576,
      "presentationToGrossExclusive": 50268,
      "sampleGross": 12576,
      "marginalIncomeTax": 0.2,
      "marginalEmployeeNi": 0.08,
      "marginalCombined": 0.28,
      "keepOfNextPound": 0.72,
      "presentationLabel": "rest_of_uk £12576–£50267: ~20% IT + ~8% NI = ~28% combined marginal IT+NI",
      "note": "rest_of_uk £12576–£50267: ~20% IT + ~8% NI = ~28% combined marginal IT+NI | engine £1-bump sample from £12576 (at £12576)"
    },
    {
      "region": "rest_of_uk",
      "fromGrossInclusive": 50268,
      "toGrossExclusive": 50270,
      "presentationFromGrossInclusive": 50268,
      "presentationToGrossExclusive": 50270,
      "sampleGross": 50268,
      "marginalIncomeTax": 0.2,
      "marginalEmployeeNi": 0.02,
      "marginalCombined": 0.22,
      "keepOfNextPound": 0.78,
      "presentationLabel": "rest_of_uk £50268–£50269: ~20% IT + ~2% NI = ~22% combined marginal IT+NI",
      "note": "rest_of_uk £50268–£50269: ~20% IT + ~2% NI = ~22% combined marginal IT+NI | engine £1-bump sample from £50268 (at £50268)"
    },
    {
      "region": "rest_of_uk",
      "fromGrossInclusive": 50270,
      "toGrossExclusive": 100000,
      "presentationFromGrossInclusive": 50270,
      "presentationToGrossExclusive": 100000,
      "sampleGross": 50270,
      "marginalIncomeTax": 0.4,
      "marginalEmployeeNi": 0.02,
      "marginalCombined": 0.42,
      "keepOfNextPound": 0.58,
      "presentationLabel": "rest_of_uk £50270–£99999: ~40% IT + ~2% NI = ~42% combined marginal IT+NI",
      "note": "rest_of_uk £50270–£99999: ~40% IT + ~2% NI = ~42% combined marginal IT+NI | engine £1-bump sample from £50270 (at £50270)"
    },
    {
      "region": "rest_of_uk",
      "fromGrossInclusive": 100000,
      "toGrossExclusive": 125140,
      "presentationFromGrossInclusive": 100000,
      "presentationToGrossExclusive": 125140,
      "sampleGross": 100000,
      "marginalIncomeTax": 0.6,
      "marginalEmployeeNi": 0.02,
      "marginalCombined": 0.62,
      "keepOfNextPound": 0.38,
      "presentationLabel": "Rest of UK: on additional employment income above £100,000 and through the Personal Allowance taper — combined marginal IT+NI ~62% (not an overall tax rate on the whole £100,000)",
      "note": "Rest of UK: on additional employment income above £100,000 and through the Personal Allowance taper — combined marginal IT+NI ~62% (not an overall tax rate on the whole £100,000) | engine £1-bump sample from £100000 (at £100000)"
    },
    {
      "region": "rest_of_uk",
      "fromGrossInclusive": 125140,
      "toGrossExclusive": 200001,
      "presentationFromGrossInclusive": 125140,
      "presentationToGrossExclusive": 200001,
      "sampleGross": 125140,
      "marginalIncomeTax": 0.45,
      "marginalEmployeeNi": 0.02,
      "marginalCombined": 0.47,
      "keepOfNextPound": 0.53,
      "presentationLabel": "rest_of_uk £125140–£200000: ~45% IT + ~2% NI = ~47% combined marginal IT+NI",
      "note": "rest_of_uk £125140–£200000: ~45% IT + ~2% NI = ~47% combined marginal IT+NI | engine £1-bump sample from £125140 (at £125140)"
    },
    {
      "region": "scotland",
      "fromGrossInclusive": 0,
      "toGrossExclusive": 12570,
      "presentationFromGrossInclusive": 0,
      "presentationToGrossExclusive": 12570,
      "sampleGross": 0,
      "marginalIncomeTax": 0,
      "marginalEmployeeNi": 0,
      "marginalCombined": 0,
      "keepOfNextPound": 1,
      "presentationLabel": "scotland £0–£12569: ~0% IT + ~0% NI = ~0% combined marginal IT+NI",
      "note": "scotland £0–£12569: ~0% IT + ~0% NI = ~0% combined marginal IT+NI | engine £1-bump sample from £0 (at £0)"
    },
    {
      "region": "scotland",
      "fromGrossInclusive": 12570,
      "toGrossExclusive": 12576,
      "presentationFromGrossInclusive": 12570,
      "presentationToGrossExclusive": 12576,
      "sampleGross": 12570,
      "marginalIncomeTax": 0.19,
      "marginalEmployeeNi": 0,
      "marginalCombined": 0.19,
      "keepOfNextPound": 0.81,
      "presentationLabel": "scotland £12570–£12575: ~19% IT + ~0% NI = ~19% combined marginal IT+NI",
      "note": "scotland £12570–£12575: ~19% IT + ~0% NI = ~19% combined marginal IT+NI | engine £1-bump sample from £12570 (at £12570)"
    },
    {
      "region": "scotland",
      "fromGrossInclusive": 12576,
      "toGrossExclusive": 16537,
      "presentationFromGrossInclusive": 12576,
      "presentationToGrossExclusive": 16537,
      "sampleGross": 12576,
      "marginalIncomeTax": 0.19,
      "marginalEmployeeNi": 0.08,
      "marginalCombined": 0.27,
      "keepOfNextPound": 0.73,
      "presentationLabel": "scotland £12576–£16536: ~19% IT + ~8% NI = ~27% combined marginal IT+NI",
      "note": "scotland £12576–£16536: ~19% IT + ~8% NI = ~27% combined marginal IT+NI | engine £1-bump sample from £12576 (at £12576)"
    },
    {
      "region": "scotland",
      "fromGrossInclusive": 16537,
      "toGrossExclusive": 29526,
      "presentationFromGrossInclusive": 16537,
      "presentationToGrossExclusive": 29526,
      "sampleGross": 16537,
      "marginalIncomeTax": 0.2,
      "marginalEmployeeNi": 0.08,
      "marginalCombined": 0.28,
      "keepOfNextPound": 0.72,
      "presentationLabel": "scotland £16537–£29525: ~20% IT + ~8% NI = ~28% combined marginal IT+NI",
      "note": "scotland £16537–£29525: ~20% IT + ~8% NI = ~28% combined marginal IT+NI | engine £1-bump sample from £16537 (at £16537)"
    },
    {
      "region": "scotland",
      "fromGrossInclusive": 29526,
      "toGrossExclusive": 43662,
      "presentationFromGrossInclusive": 29526,
      "presentationToGrossExclusive": 43663,
      "sampleGross": 29526,
      "marginalIncomeTax": 0.21,
      "marginalEmployeeNi": 0.08,
      "marginalCombined": 0.29,
      "keepOfNextPound": 0.71,
      "presentationLabel": "Scotland Intermediate through £43,662: combined marginal IT+NI ~29% (21%+8%)",
      "note": "Scotland Intermediate through £43,662: combined marginal IT+NI ~29% (21%+8%) | engine £1-bump sample from £29526 (at £29526)"
    },
    {
      "region": "scotland",
      "fromGrossInclusive": 43662,
      "toGrossExclusive": 50268,
      "presentationFromGrossInclusive": 43663,
      "presentationToGrossExclusive": 50268,
      "sampleGross": 43662,
      "marginalIncomeTax": 0.42,
      "marginalEmployeeNi": 0.08,
      "marginalCombined": 0.5,
      "keepOfNextPound": 0.5,
      "presentationLabel": "Scotland Higher Rate from £43,663 through around £50,270 (before higher employee NI): combined marginal IT+NI ~50% (42%+8%); keep ~50p of the next £1",
      "note": "Scotland Higher Rate from £43,663 through around £50,270 (before higher employee NI): combined marginal IT+NI ~50% (42%+8%); keep ~50p of the next £1 | engine £1-bump sample from £43662 (at £43662)"
    },
    {
      "region": "scotland",
      "fromGrossInclusive": 50268,
      "toGrossExclusive": 75000,
      "presentationFromGrossInclusive": 50268,
      "presentationToGrossExclusive": 75001,
      "sampleGross": 50268,
      "marginalIncomeTax": 0.42,
      "marginalEmployeeNi": 0.02,
      "marginalCombined": 0.44,
      "keepOfNextPound": 0.56,
      "presentationLabel": "Scotland Higher Rate after employee NI UEL (~around £50,270) to Advanced: combined marginal IT+NI ~44% (42%+2%)",
      "note": "Scotland Higher Rate after employee NI UEL (~around £50,270) to Advanced: combined marginal IT+NI ~44% (42%+2%) | engine £1-bump sample from £50268 (at £50268)"
    },
    {
      "region": "scotland",
      "fromGrossInclusive": 75000,
      "toGrossExclusive": 100000,
      "presentationFromGrossInclusive": 75001,
      "presentationToGrossExclusive": 100000,
      "sampleGross": 75000,
      "marginalIncomeTax": 0.45,
      "marginalEmployeeNi": 0.02,
      "marginalCombined": 0.47,
      "keepOfNextPound": 0.53,
      "presentationLabel": "scotland £75001–£99999: ~45% IT + ~2% NI = ~47% combined marginal IT+NI",
      "note": "scotland £75001–£99999: ~45% IT + ~2% NI = ~47% combined marginal IT+NI | engine £1-bump sample from £75000 (at £75000)"
    },
    {
      "region": "scotland",
      "fromGrossInclusive": 100000,
      "toGrossExclusive": 125140,
      "presentationFromGrossInclusive": 100000,
      "presentationToGrossExclusive": 125140,
      "sampleGross": 100000,
      "marginalIncomeTax": 0.675,
      "marginalEmployeeNi": 0.02,
      "marginalCombined": 0.695,
      "keepOfNextPound": 0.305,
      "presentationLabel": "Scotland: on additional employment income above £100,000 and through the Personal Allowance taper — combined marginal IT+NI ~69.5% (not an overall tax rate on the whole £100,000)",
      "note": "Scotland: on additional employment income above £100,000 and through the Personal Allowance taper — combined marginal IT+NI ~69.5% (not an overall tax rate on the whole £100,000) | engine £1-bump sample from £100000 (at £100000)"
    },
    {
      "region": "scotland",
      "fromGrossInclusive": 125140,
      "toGrossExclusive": 200001,
      "presentationFromGrossInclusive": 125140,
      "presentationToGrossExclusive": 200001,
      "sampleGross": 125140,
      "marginalIncomeTax": 0.48,
      "marginalEmployeeNi": 0.02,
      "marginalCombined": 0.5,
      "keepOfNextPound": 0.5,
      "presentationLabel": "scotland £125140–£200000: ~48% IT + ~2% NI = ~50% combined marginal IT+NI",
      "note": "scotland £125140–£200000: ~48% IT + ~2% NI = ~50% combined marginal IT+NI | engine £1-bump sample from £125140 (at £125140)"
    }
  ]
}