Yes, and that is what it is designed for. One integration and one set of API credentials cover as many employers and PAYE schemes as you need. Managing dozens of client companies on one integration is the normal case.
How are employers kept apart?
Every resource sits under its employer, at /api/employer/{employer_pk}/..., so employers are isolated by the structure of the API rather than by convention. Each employer carries its own PAYE reference, Accounts Office reference, Government Gateway credentials and RTI submission settings, and can run several pay schedules at once.
Is there a view across all our employers?
Yes, for bureau accounts. GET /api/employer/bureau-usage/ returns aggregate figures across every employer the account manages: total employers, total employees, and finalised versus open payruns in each employer's current tax year.
Get started
Request a sandbox key at https://www.moonworkers.co.uk/api. The Employer section of the reference is at https://payroll-api.moonworkers.co.uk/api/redoc/#tag/Employer.