OnPay is a software company based in the United States, specializing in human resources and finance software solutions. Founded in 2011, the company employs between 51 and 200 staff members and has reported revenue of approximately $16.3 million. OnPay's expertise lies in providing payroll management services, as evidenced by their published document, which outlines a detailed checklist for accountants managing mid-year payroll transitions. This document emphasizes the importance of evaluating new payroll providers for their compatibility with specific client needs, including pay schedules, tax situations, and integration with existing HR and accounting tools. It also details the necessary steps for data migration, employee communication, and compliance with multi-state tax regulations. The focus on practical guidance for accountants indicates OnPay's commitment to facilitating seamless payroll processes for businesses, highlighting its role in the broader software landscape within human resources and finance sectors.