UK Payroll API
The UK payroll engine
your platform is missing.
Add a complete, HMRC-compliant UK payroll engine to your ERP, HR platform or workforce tool via a single REST API. Employees, pay runs, RTI submissions and statutory obligations, all handled for you.
Multiple employers and pay schedules
Manage unlimited employer entities under a single integration. Run parallel pay schedules of any frequency, including multiple weekly or monthly schemes simultaneously.
Complete UK payroll engine
PAYE, NI, directors, CIS subcontractors, zero-hours and variable workers all handled. RTI submissions fire automatically on every pay run, no manual steps.
HMRC document schemas included
Payslip PDFs, P60, P45, P11D and CIS300 deduction statements all generated and served via API. No third-party document service required.
Statutory pay and auto-enrolment
SMP, SSP, SPP, ShPP and SAP calculated automatically. Pension auto-enrolment assessment, contribution splits and opt-out handling built into every pay run.
Trusted by UK businesses and accountancy firms
Employers and Employees
Multiple entities.
One integration.
Model your entire customer base in the API. Each employer gets its own payroll, employees and document history. Onboard a new worker with a single POST, the API validates everything before it touches compliance.
Multiple employers, one integration
Create and manage unlimited employer entities. Run payroll for each entity independently while keeping all data under a single API key.
Every UK employment type
Employee, director, IR35 deemed employee, CIS subcontractor and agency worker, all supported. NI and tax code validation rejects bad data before it reaches HMRC.
Idempotent creation
Pass your own external ID and re-POST safely. Duplicate records are never created from retry logic, making bulk onboarding safe.
Request body
Response
201 CreatedRequest body
Response
201 CreatedPay run summary — run_9x4wlk82
£7,583.33
Gross
£1,204.60
PAYE
£721.14
NI
£5,657.59
Net pay
Pay schedules and Pay runs
Run payroll.
RTI fires itself.
Define as many pay schedules as your customers need, monthly, weekly, multiple of the same, all in parallel. Trigger a pay run and the API handles every calculation, every deduction and every HMRC submission.
Parallel pay schedules, any frequency
Run multiple weekly, fortnightly or monthly pay schedules simultaneously, including several schedules of the same frequency within one employer, all processed independently.
RTI submitted automatically
Every pay run fires a Full Payment Submission to HMRC automatically. No manual RTI step, no third-party gateway. Employer Payment Summaries are handled on the same basis.
PAYE, NI and pension calculated
Tax and NI are computed per HMRC rates. Auto-enrolment pension contributions are assessed and included for eligible employees on every run.
Payslips, Documents and CIS
Every HMRC document.
One API.
Retrieve any payroll document, payslip, P60, P45, P11D, or CIS statement, as structured JSON or a ready-to-download PDF. Store them in your document management system or surface them in your own UI.
Payslip PDF and JSON from one endpoint
Every payslip is available as a machine-readable JSON breakdown and a print-ready HMRC-compliant PDF, available immediately after the pay run completes.
P60, P45, P11D and year-end documents
End-of-year P60s and leaver P45s are generated automatically. P11D benefit-in-kind documents and year-end submissions are handled through the same resource pattern.
CIS300 and subcontractor deduction statements
Construction Industry Scheme monthly returns are filed automatically alongside PAYE. Subcontractor deduction statements are generated per payment run.
Response
200 OKPay breakdown
Request body
Response
201 CreatedHoliday entitlement, Sarah Mitchell
2026/27 tax yearLeave and Statutory Pay
Absence managed.
Payroll updated.
Create and manage all leave types through the API. Statutory entitlement is tracked automatically. SMP, SSP, SPP, ShPP and SAP are calculated and built into the next pay run without any manual intervention.
Annual leave with 52-week average pay
Statutory 28-day allowance tracked per employee per tax year. Holiday pay for variable-hours workers is computed on a 52-week average basis, fully ERA-compliant.
All statutory leave and pay types
SMP (Statutory Maternity Pay), SSP (Sick Pay), SPP (Paternity), ShPP (Shared Parental) and SAP (Adoption Pay) are all calculated and incorporated into the pay run automatically.
Approval workflow via API
Submit, approve or reject leave requests programmatically. Build your own approval UI on top or route through an existing HR workflow, with holiday pay factored in automatically at payrun time.
Pensions and Auto-enrolment
Workplace pensions.
Zero manual steps.
Auto-enrolment is assessed on every pay run. Contributions are calculated, deducted and surfaced in payslip data automatically. Opt-outs, re-enrolments and postponements are all handled by the API.
Auto-enrolment assessment on every run
Workers are assessed for eligibility at each pay run. Newly eligible employees are enrolled automatically, with confirmation returned in the pay run response.
Contribution splits calculated
Employer and employee pension contributions are computed on qualifying earnings, deducted from net pay and broken down in both the payslip JSON and PDF. Rates are configurable per employer.
Opt-out and postponement handled
Process opt-out requests and re-enrolment windows through the API. Postponement periods are tracked per worker and enrolment is triggered automatically when the window closes.
Response
200 OKContribution breakdown
Auto-enrolment status
enrolledYes
Eligible
No
Opted out
None
Postponement
Who integrates
Built for platforms
that build for business.
Whether you are embedding payroll into an ERP, connecting a people platform, or building a bespoke payroll flow, the Moonworkers API gives you the full UK payroll engine through a single integration.
ERP & accounting platforms
Add native UK payroll without building a payroll engine.
- Embed compliant payroll directly inside your ERP module
- RTI submissions handled by Moonworkers, zero compliance overhead
- Map your own employee and ledger IDs to Moonworkers resources
HR & people platforms
Connect your HRIS to a compliant UK payroll backend.
- Sync employee records from your HRIS on every change
- Push leave approvals and trigger holiday pay automatically
- Serve payslip PDFs directly inside your employee self-service portal
Workforce & staffing platforms
Pay contractors, temp workers and shift staff via API.
- Variable hours and daily-rate workers handled natively
- CIS subcontractor payments with correct deductions
- Run payroll for individual workers without a full payroll subscription
In-house development teams
Build a bespoke payroll flow for your organisation.
- OpenAPI schema and ReDoc reference documentation included
- Webhook events for every pay run, payslip and RTI status change
- Staging environment for end-to-end integration testing
99.9%
Uptime SLA
<120ms
Median response time
40+
API endpoints
100%
RTI acceptance rate
Our customers say it best.
From sole traders to growing enterprises, teams across the UK rely on Moonworkers to run payroll without the headache.
JC Puget
Maison Puget
“The best payroll company for my business. Highly recommend.”
S Djakiodine
Euroaccounting
“We have been using Moonworkers for quite some time and compared to other software in the market, we found it very simple to use and excellent. Moreover, the customer service is great.”
Shenaz Gaffar
Printberry
“Moonworkers has absolutely been a lifesaver for me and my business. Moonworkers customer service is 100% there always there to help. They constantly taking on feedback to make it better. If you are looking to make life easier, then this is it !!!”
Joe Barber
The Barn
“Fantastic onboarding process from the team. A really user friendly website and system. When I have asked for any assistance or help, the team have helped, made changes and even updated the system for my requests!”
James Berry
CJLS Tech
“From the outset the onboarding to Moonworkers was 100% smooth, even any hints of a problem were speedily fixed and we have been running smoothly since then, we have never needed to reach out to support post onboarding, and that's a testament to its own.”
Suzy Kerton
Zyla Accountant
“Moonworkers software is great for HR, payroll, benefits & more and it is amazing to have it all in one platform. The automation saves so much time every month and the team offer great customer support whenever you have a query. Highly recommend!”
Amrit Gill
Hayachi
“Incredibly powerful HR and Payroll platform, we've previously been held back by our accountant on having a truly flexible workforce but no more! With Moonworkers we can hire the skills that we need with exceptional efficiency and the HR platform makes it a well-rounded tool.”
Row Laurence
Braid
“The Moonworkers platform has been a massive help getting me set up with my first few employees and making sure I had all the right boxes ticked – the team have also been super helpful and responsive any time I had questions or there was something I didn't understand.”
Ready to integrate?
UK payroll in your platform
without building the engine.
Read the full API reference, request a sandbox key, or speak to the team about a production integration. Most teams are live within a week.