You can enter multiple transactions for an employee within the same period (using the same Period ID), such as a timesheet and a manual calculation. This will create multiple pay advices.
However, if transactions are processed in different periods that share the same Period End Date, not all pay advices will be available. For example, if you complete End of Pay for 15 September and then reuse 15 September as the Period End Date in the next period.
Each of the periods will have a different Period ID (you can see this in Employee Enquiries or IQ reports), but as the Period End Date is the same, the most recent Pay Advice produced will override the previous one. Meaning that employees will only see one in ESS.
To avoid this, we recommend that you use a different period end date for each period i.e., 15 September and 16 September.