If your organization has made a decision to migrate your United Kingdom (UK) payroll processing to new payroll vendor you should not change the Employee ID Numbers. It is highly recommended that you continue using the same Employee ID Numbers used with the existing payroll vendor. If you do not, this will create a second employee record per employee with HMRC (the UK Revenue) and will lead to many PAYE under/overpayment issues. The below website from HMRC confirms the need to report Employee number/ID changes in the RTI FPS Submission (please refer to the Employee Information section):

https://www.gov.uk/guidance/what-payroll-information-to-report-to-hmrc#employee-information

Employer alerts are provided by Kira Rubiano, Sr. Partner Management Specialist – Europe/Asia Pac.