|You will get this error when you carry out payroll activities in the Bureau / Client without logging out after you initiated the "Start New Tax Year" process.
Please remember that after you Confirm "Start New Tax Year" by Clicking on the Start New Tax Year button,
you should sign out and sign in to ensure that you are indeed in the New Tax Year and then resume all payrun activities.
This is required since when you start a new tax year, data in the previous tax year is frozen and cannot be changed or rolled back.
If you ignore the "Start New Tax Year" warning and go about performing payroll activities such as creating new employees without signing out and signing in, then you will get this FT5518 error when you process payrun for such employees at a later point of time.
In that case you need to delist the employees and recreate them in the current tax year to be able to process the pay without any issues.