A Pay Run is the date when you will disburse salaries to your employees.  It will always correspond to a designated Pay Period, which you can determine when you set up a payroll group.  You can view the dates of your pay runs and corresponding pay periods in the payroll calendar for the payroll group.

The number of pay runs in a month will depend on the Pay Frequency of your payroll group.  A payroll group with a monthly pay frequency will have one pay run, a payroll group with a semi-monthly pay frequency will have two pay runs and payroll groups with either weekly or fortnightly pay frequencies will have pay runs corresponding to how many weeks or fortnights there are during the month.

To determine your pay run dates, go to Company Setup>Payroll>Payroll Group>Add Payroll Group. The Payroll Group creation page will pop up.  Select the payroll group Pay Frequency, and the pay run date field will pop up.  You can enter your pay run dates here.

For payroll groups with monthly, weekly or fortnightly pay frequencies, you will only need to enter one pay run date, and the system will calculate the remaining pay run dates for the payroll group.  For payroll groups with semi-monthly pay frequencies, you will need to enter both the first and second pay run dates for the month.  The system will calculate the remaining pay run dates for the payroll group based on the dates you enter.