You can create your own variable pay categories to add to employee salaries when needed. The default list includes Bonus, Commission and Overtime.
To do this, follow the below mentioned steps -
Under Settings, click on Configuration and click on the Payroll tab.
Expand the Variable Pays tab and click on Add New or the Edit icon to edit any of the existing default categories.
Fill in the name of your new variable pay category and click on Save.
The list of variable pay categories will be visible on an employee's Active Payroll Month under the Payroll tab on their profile (also accessible by clicking on employee row on the payroll table).