# Build on PayCaptain

> One API for UK payroll data. Send employees, shifts and pay elements in; read employees and payslips out. Every rule is published here, for people and for agents.

## What you can do

| You want to | Use | Field rules |
| --- | --- | --- |
| Create or update an employee | `POST /employee` | [Employee fields](https://developer.paycaptain.com/fields/employee) |
| Send approved shifts and absences | `POST /shift` | [Shift fields](https://developer.paycaptain.com/fields/shift) |
| Send bonuses, expenses and other pay elements | `POST /payment` | [Payment fields](https://developer.paycaptain.com/fields/payment) |
| Read employees back | `GET /employees` | [Employee fields](https://developer.paycaptain.com/fields/employee) |
| Read payslips for a pay period | `GET /payslips` | [Payslip fields](https://developer.paycaptain.com/fields/payslip) |

New here? The [Quickstart](https://developer.paycaptain.com/quickstart) takes you from API key to first accepted record.

## How it fits together

Your application is the system of record for people, attendance and pay elements. PayCaptain is the payroll engine. Records flow one way, through a validation layer you own, and payslips flow back.

```text
Your application  ->  Your validation layer  ->  PayCaptain
employees             field rules                POST /employee
shifts                business rules             POST /shift
pay elements          change detection           POST /payment
payslip viewer   <-   ------------------------   GET /payslips, GET /employees
```

> **Must** Validate before you send. PayCaptain rejects invalid data, but it is not your validation service. Enforce the [field rules](https://developer.paycaptain.com/fields/employee) and [business rules](https://developer.paycaptain.com/rules) in your own code, and only then call the API.

## Trust, in practice

PayCaptain is HMRC-recognised payroll software with a direct connection to UK banking services, certified to ISO 27001 and Cyber Essentials Plus. Payroll only works when everyone can rely on it, so this site is built to be checked rather than believed.

- **Every rule is written down.** Each field has its type, format, allowed values and conditions on one page. If the API rejects something for a reason that is not documented here, tell us and we will document it.
- **One source for people and agents.** Every page is also plain Markdown, and the field rules ship as JSON Schema and OpenAPI. All of it is generated from the same data, so the copies cannot drift apart.
- **Clear responsibilities.** PayCaptain's core is operated by PayCaptain UK personnel. Your integration comes in through one authenticated door, and [Trust and security](https://developer.paycaptain.com/trust) sets out what we do and what you must do.
- **No trackers on this site.** No cookies, no analytics scripts, no third-party requests.

## Open to the way you work

- **Customers** connect the HR, rota and time systems they already run, or build their own.
- **Payroll teams** stay in control. Pay Groups, Pay Codes and approvals are configured in PayCaptain, and the API respects them.
- **Partners** build one integration and offer it to every shared customer.
- **AI builders and agents** get the same rules in machine-readable form. See [Build with AI](https://developer.paycaptain.com/agents).

More endpoints are available on request. Email [developer@paycaptain.com](mailto:developer@paycaptain.com) to discuss what you need, or to get your API key and company code.