How can I change dates for the email notifications to employees and business users in closed pay runs?
If you already closed the pay run, you will have to reopen the pay run in order to be able to change these dates. Reopening pay runs is done in Process/Reopen pay runs.
We advise to always set a notification date when finalizing/closing a (not yet approved) payroll, because if afterwards the payroll seems to be error-less (which will often occur in Celery ;) and approved, you do not have to do anything anymore because you already set the notification dates.