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Documentation Index

Fetch the complete documentation index at: https://docs.flowpayroll.ai/llms.txt

Use this file to discover all available pages before exploring further.

The Flow Payroll API lets you automate payroll management programmatically: configure pay runs, manage employees and clients, upload payroll data, calculate gross-to-net, generate payslips, and stay HMRC-compliant through RTI submissions. The API follows REST principles, uses JSON for requests and responses, and wraps every response in a consistent envelope.
Need a client_id / client_secret? See Authentication. Want the whole surface in one file for Postman or Insomnia? See Use in Postman.

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Base URLs

Each service is reached through the API gateway under a versioned path. The core Pay API lives at /v1; every other domain has its own /v1/<service> (or /v2/<service>) prefix.
EnvironmentBase URL
Sandboxhttps://api.sandbox.flowpayroll.ai
Livehttps://api.flowpayroll.ai
Always build and test against sandbox first. Sandbox data is isolated from live and safe to experiment with.

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API families

The reference is grouped by service. Each group below is generated directly from that service’s OpenAPI specification.

Pay API

The core of payroll: employees, payroll runs, the gross-to-net calculator, payslips, and RTI (FPS & EPS).

Statutory pay

Calculate and record SSP, SMP, SPP, ShPP, SAP and more, with average-earnings checks and reconciliation.

Court orders

Attachment of earnings — CMS DEO, AEO, DEA, CTAEO and others — plus payees and protected-earnings handling.

Holiday & leave

Leave records, opening balances, accrual configuration, and average holiday-pay history.

Pensions

Auto-enrolment assessment, schemes, providers, groups, calculations, exports and enrolment letters.

Recurring line items

Recurring pay and deduction items, their periods, and skip/patch operations.

HMRC DPS

Retrieve and apply HMRC Data Provisioning Service notifications (tax codes, student loans, and more).

HMRC P-forms

Generate statutory forms such as the P45.

Billing

Clients, invoices, credit notes, finance settings, and accounting-provider sync.

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A typical payroll run

1

Configure

Create a payroll configuration with POST /payrollconfig (pay frequency and settings).
2

Add people

Add employees with POST /employee, and clients with POST /client if you run payroll for multiple entities.
3

Upload pay data

Send pay and deduction lines with POST /payroll/upload.
4

Preview

Preview payslips at any time with GET /payslip/data/{employeeId}/{year}/{period} — even outside the configured frequency.
5

Lock & submit

Lock the period to generate final payslips, then submit the FPS to HMRC. Submit the EPS at month-end.

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Conventions

  • Organisation scoping — every resource belongs to an organisation, which is derived from your credentials. You never pass an organisation ID in the request body.
  • IDs — resources use ULID-based identifiers.
  • Dates — ISO‑8601. Response metadata states the exact dateFormat and dateTimeFormat in use.
  • Pagination — list endpoints are paginated; page through large result sets rather than requesting everything at once.

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Support

Stuck on an endpoint? Email hello@flowpayroll.ai.