> An API that runs one UK pay period like payroll software: cumulative or week 1/month 1 tax, NI by category letter, directors’ NI and student loans.

Web version: https://checktakehomepay.co.uk/payroll-api · Last updated: 2026-10-09

[API](https://checktakehomepay.co.uk/api) / Payroll

# Payroll calculation API

Short answer

One pay period exactly as payroll software runs it: tax on a cumulative or week 1/month 1 code, employee and employer NI by category letter (directors on the annual earnings period), student loans and the NI earnings bands for RTI.

-   HMRC’s 2026/27 payroll test cases for income tax, NI, directors’ NI and student loans run through this endpoint, to the penny.
-   All 16 NI category letters, Freeport and Investment Zone ones included.

## Endpoints

-   `POST /v1/payroll/period`Tax, NI and student loans for a period
-   `GET /v1/rates`Every rate and threshold (no key)

## Try a request

Money is pounds and pence. Every response carries the tax year, the engine and HMRC test data that produced it, the assumptions and the gov.uk sources.

```
curl https://api.checktakehomepay.co.uk/v1/payroll/period \
  -H "Authorization: Bearer $CHECKTAKEHOMEPAY_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{
  "pay_frequency": "monthly",
  "period": 1,
  "tax_code": "1257L",
  "gross_pay": 3000
}'
```

## Questions

### Can I use it instead of a payroll tax table?

Yes: it follows HMRC’s PAYE tax table routines and NI guidance for software developers, and passes HMRC’s own test cases.

## Put it in your software

Every endpoint on every plan, from the free one up.

[Get an API key](https://checktakehomepay.co.uk/login)[Read the quickstart](https://checktakehomepay.co.uk/docs/quickstart)