IsMyPayRight API
Programmatic access to accurate UK PAYE tax calculations. The same engine that powers ismypayright.co.uk, available as a simple REST API.
Quick Start
No API key needed for the free tier — just send a request:
curl -X POST https://ismypayright.co.uk/api/v1/calculate \
-H "Content-Type: application/json" \
-d '{
"salary": 50000,
"taxYear": "2025-26",
"region": "england",
"frequency": "year"
}'Example response
{
"data": {
"grossAnnual": 50000,
"personalAllowance": 12570,
"taxableIncome": 37430,
"incomeTax": {
"totalTax": 7486,
"effectiveRate": 0.14972,
"marginalRate": 0.2,
"bands": [
{ "name": "Basic rate", "rate": 0.2, "taxable": 37430, "tax": 7486 }
]
},
"nationalInsurance": {
"employee": { "totalContribution": 2994.4, "effectiveRate": 0.059888 }
},
"totalDeductions": 10480.4,
"netAnnual": 39519.6,
"effectiveTaxRate": 0.209608,
"marginalTaxRate": 0.28,
"breakdown": {
"monthly": {
"gross": 4166.67, "incomeTax": 623.83,
"nationalInsurance": 249.53, "net": 3293.3
}
}
},
"meta": {
"version": "1",
"taxYear": "2025-26",
"calculatedAt": "2026-04-04T13:12:00.000Z"
}
}Endpoints
Full API docs →/api/v1/health
Health check — returns API status and available tax years
/api/v1/calculate
Full PAYE calculation — income tax, NI, student loans, pension, salary sacrifice
/api/v1/check
Validate payslip figures against expected HMRC calculations
/api/v1/reverse
Reverse-calculate the gross salary needed for a target net pay
/api/v1/pro-rata
Pro-rata salary by hours, days, or date range
/api/v1/two-jobs
Combined tax calculation for two jobs with NI overpayment estimates
/api/v1/statutory-pay
SMP, SSP, and SPP weekly schedules with tax estimates
/api/v1/mortgage
Mortgage affordability — borrowing range, repayments, stress test
Authentication
Free Tier
10 requests per hour, no API key needed. Perfect for evaluation and small projects.
API Key
Higher rate limits and usage tracking. Pass your key as a Bearer token in the Authorization header.
Ready to integrate?
Get an API key for higher rate limits and priority support.