Free UK Tax Calculation API

A free, read-only REST API for UK income tax calculations using 2025-26 HMRC rates. Calculate income tax, National Insurance, student loan repayments and take-home pay for any salary.

Status

Live

2025-26 rates

Auth required

None

Fully public

Rate limits

None

Please cache responses

Format

JSON

CORS enabled

Endpoint

GET https://calculatetax.uk/api/calculate

Query Parameters

Parameter	Type	Required	Default	Description
gross	number	Yes	,	Annual gross salary in GBP (0-10,000,000)
region	string	No	england	england, scotland, wales, northern-ireland
studentLoan	string	No	none	none, plan1, plan2, plan4, plan5, postgrad
pensionPercent	number	No	0	Pension contribution as percentage of gross (0-100)
hoursPerWeek	number	No	37.5	Working hours per week, affects netHourly only (1-168)

Example Request

Calculate take-home pay for a £35,000 salary in England:

GET https://calculatetax.uk/api/calculate?gross=35000

With optional parameters (Scotland, Plan 2 student loan, 5% pension):

GET https://calculatetax.uk/api/calculate?gross=35000®ion=scotland&studentLoan=plan2&pensionPercent=5

Example Response

Response for ?gross=35000®ion=england, 200 OK

{
  "gross": 35000,
  "region": "england",
  "personalAllowance": 12570,
  "taxableIncome": 22430,
  "incomeTax": 4486,
  "nationalInsurance": 1794,
  "studentLoanRepayment": 0,
  "pensionContribution": 0,
  "totalDeductions": 6280,
  "netPay": 28720,
  "netMonthly": 2393,
  "netWeekly": 552,
  "netDaily": 110,
  "netHourly": 14.73,
  "effectiveTaxRate": 17.94,
  "marginalTaxRate": 28,
  "employerNI": 4500,
  "totalCostToEmployer": 39500,
  "breakdown": {
    "incomeTaxBands": [
      {
        "name": "Personal Allowance",
        "rate": 0,
        "from": 0,
        "to": 12570,
        "taxableInBand": 12570,
        "taxInBand": 0
      },
      {
        "name": "Basic Rate (20%)",
        "rate": 0.2,
        "from": 12570,
        "to": 50270,
        "taxableInBand": 22430,
        "taxInBand": 4486
      },
      {
        "name": "Higher Rate (40%)",
        "rate": 0.4,
        "from": 50270,
        "to": 125140,
        "taxableInBand": 0,
        "taxInBand": 0
      },
      {
        "name": "Additional Rate (45%)",
        "rate": 0.45,
        "from": 125140,
        "to": null,
        "taxableInBand": 0,
        "taxInBand": 0
      }
    ],
    "niBands": [
      {
        "name": "Below Primary Threshold",
        "rate": 0,
        "from": 0,
        "to": 12570,
        "earningsInBand": 12570,
        "niInBand": 0
      },
      {
        "name": "Main Rate (8%)",
        "rate": 0.08,
        "from": 12570,
        "to": 50270,
        "earningsInBand": 22430,
        "niInBand": 1794
      },
      {
        "name": "Upper Rate (2%)",
        "rate": 0.02,
        "from": 50270,
        "to": null,
        "earningsInBand": 0,
        "niInBand": 0
      }
    ]
  },
  "_meta": {
    "note": "calculatetax.uk API, 2025-26 HMRC rates. Free to use. Please cache responses.",
    "taxYear": "2025-26",
    "source": "https://calculatetax.uk"
  }
}

Response Fields

Field	Type	Description
gross	number	Annual gross salary (echoed from input)
personalAllowance	number	Tax-free personal allowance (tapers above £100,000)
taxableIncome	number	Gross minus personal allowance and pension
incomeTax	number	Annual income tax liability
nationalInsurance	number	Employee NI contributions (Class 1)
studentLoanRepayment	number	Annual student loan repayment (0 if no plan)
pensionContribution	number	Annual pension contribution (salary sacrifice)
totalDeductions	number	Sum of all deductions from gross
netPay	number	Annual take-home pay
netMonthly	number	Monthly take-home pay (netPay / 12)
netWeekly	number	Weekly take-home pay (netPay / 52)
netDaily	number	Daily take-home pay (netPay / 260 working days)
netHourly	number	Hourly take-home pay (based on hoursPerWeek)
effectiveTaxRate	number	Combined IT + NI as percentage of gross
marginalTaxRate	number	Combined marginal rate on next pound earned (%)
employerNI	number	Employer NI at 15% above £5,000 secondary threshold
totalCostToEmployer	number	Gross plus employer NI
breakdown	object	Detailed band-by-band breakdown of income tax and NI

Error Responses

All errors return a JSON object with an error field and the appropriate HTTP status code.

Status	Cause	Example error message
400	Missing or invalid parameter	Missing required parameter: gross
400	Gross out of range	Invalid gross: must be a number between 0 and 10,000,000
400	Unknown region	Invalid region: must be one of england, scotland, wales, northern-ireland

Example error response (400):

{"error":"Missing required parameter: gross"}

Usage Notes

All monetary values in the response are in GBP (£), rounded to the nearest pound, except netHourly which is rounded to 2 decimal places.
Rates reflect 2025-26 HMRC rates. The API will be updated each tax year.
Pension contributions are treated as salary sacrifice (reduces taxable income but not NI earnings).
The breakdown object includes per-band income tax and NI details useful for building tax calculators.
Responses are cached with Cache-Control: public, max-age=3600. Please cache on your end too.
Currently free with no rate limits. Subscribe to updates if you depend on this API.

Rate Limits & Updates

Currently free with no rate limits. Please cache responses where possible, the underlying tax rates only change once a year (April). Responses include a 1-hour cache header.

CORS is fully enabled, you can call this API directly from the browser or any frontend application. No API key required.

Subscribe for API updates

Income Tax Rates 2025-26 National Insurance Rates £35,000 After Tax Net to Gross Calculator Tax Calculators