An RTI number, or ID, is a unique identifier used by the HMRC to keep track of your employees' tax records. You can normally find this in your previous software, FPS (full payment submission) or if you ask your accountant.
A payroll ID (also known as payroll reference number) is a unique identifier used by your company to keep track of your employees. These are usually found on the payslip.
In most cases, the RTI ID and the payroll ID of an employee are the same. However, in cases where they aren't, it's best to always double-check.
Tip: If you're adding a new employee, or running payroll for the first time, you'll need to assign a new RTI ID or payroll ID for each employee.
Do's and don'ts of RTI IDs
✅ Use the same RTI ID when switching payroll software
When migrating from one software to PayFit partway through the tax year, you must use the same RTI ID. Otherwise, HMRC treats this as a new employee and employment. This duplicates the employee's pay information and causes a discrepancy for both the employer and employee.
✅ You can use a combination of letters and numbers when creating your RTI ID / Payroll ID (e.g. PayFit001)
✅ The RTI ID can match your Payroll ID.
❌ Two employees can't have the same RTI ID You can't reuse RTI Id even after an employee has left. HMRC will use your employer details and RTI ID and will merge the two records together.
❌ Don't use the same RTI ID for an employee who has left and returned. You need to assign them a new RTI ID for their new employment.
❌ Don't assume that the payroll ID is the RTI ID. If you're not sure, you can check with your previous payroll provider or contact HMRC to ask for your RTI ID by telling them that you are switching payroll software mid-tax year.