Employee's payroll IDs for full payment submissions (FPS)
HMRC have shared a reminder that any new Payroll ID should be unique and must be different if the employee has more than one job. Do not reuse previous Payroll IDs for existing or new employees. This also applies if you change payroll software and the new software does not let you continue with the same payroll ID.
Where the old Payroll ID is not supplied, HMRC can use the financial information on the Full Payment Submission to aid matching during the year where the financial information cumulates with the previous period’s information. However, in the first period at the start of the tax year, the financial information does not aid the matching process because there is no previous period in the tax year.