{"openapi":"3.1.0","info":{"title":"CalcHub UK Tax API","version":"1.0.0","description":"Free, read-only JSON API for UK tax calculations (2026/27), powered by the same HMRC-verified engine as calchub.uk. No auth. Free with required attribution — see https://calchub.uk/api/terms/.","contact":{"name":"CalcHub.uk","url":"https://calchub.uk/api/","email":"hello@calchub.uk"},"license":{"name":"Free with attribution","url":"https://calchub.uk/api/terms/"}},"servers":[{"url":"https://calchub.uk/api/v1","description":"Production (static, pre-generated)"}],"externalDocs":{"description":"API docs","url":"https://calchub.uk/api/"},"paths":{"/take-home/{key}":{"get":{"summary":"Take-home pay","description":"Net pay after Income Tax, National Insurance and pension. Key: `<salary>-<region>`, e.g. `50000-england`.","operationId":"getTakeHome","parameters":[{"name":"key","in":"path","required":true,"description":"`<salary>-<region>` — salary £10k–£200k (£5k steps pre-generated).","schema":{"type":"string","pattern":"^\\d+-(england|scotland|wales|northern-ireland)$"},"example":"50000-england"}],"responses":{"200":{"description":"Take-home breakdown","content":{"application/json":{}}}}}},"/income-tax/{key}":{"get":{"summary":"Income Tax","description":"UK Income Tax bands (England/Wales/NI + Scotland 6-band). Key: `<income>-<region>`.","operationId":"getIncomeTax","parameters":[{"name":"key","in":"path","required":true,"schema":{"type":"string","pattern":"^\\d+-(england|scotland|wales|northern-ireland)$"},"example":"50000-scotland"}],"responses":{"200":{"description":"Income Tax breakdown","content":{"application/json":{}}}}}},"/national-insurance/{salary}":{"get":{"summary":"National Insurance","description":"Class 1 employee NI (UK-wide). Path: `<salary>`.","operationId":"getNationalInsurance","parameters":[{"name":"salary","in":"path","required":true,"schema":{"type":"integer"},"example":50000}],"responses":{"200":{"description":"NI breakdown","content":{"application/json":{}}}}}},"/stamp-duty/{key}":{"get":{"summary":"Stamp duty (SDLT/LBTT/LTT)","description":"Property purchase tax. Key: `<price>-<region>` (england=SDLT, scotland=LBTT, wales=LTT).","operationId":"getStampDuty","parameters":[{"name":"key","in":"path","required":true,"schema":{"type":"string","pattern":"^\\d+-(england|scotland|wales)$"},"example":"500000-england"}],"responses":{"200":{"description":"Stamp duty breakdown","content":{"application/json":{}}}}}}}}