There are two components to security:

Firstly, access to elements of the Payroll module can be limited to specific users. 

Secondly, information that users can see and change can also be controlled.  This security applies to data throughout the system including the payroll module, and budgeting and reporting areas.

A) Access to the Payroll Module

Access is managed on Assign User Permissions by checking the required access boxes on the User Profile tab.

1. Checking" Payroll" provides the following access, namely the ability to see the main menu :

2. Checking "Payroll" and "Payroll Setup" provides the following access:

3.  Checking "Payroll" and "Employee Roster" provides the following access:

4. Checking "Payroll" and "Payroll Data Entry" provides the following access:

Please note that the "Payroll" checkboxes on Manage Objects and Manage Budget Accounts are not security features.  Rather, checking this box makes the Object and/or Budget Account available for budgeting in the Payroll module.

Related Article/s:

What Do I Do When an Application User is Setup with Payroll Security But Does not See the Payroll Menu?

B) Access to Payroll Information

Access to view payroll information is managed in Assign User Permissions on the OrgUnit Permissions tab. 

Here users can be given access to information of an OrgUnit and that information can be controlled through the use of Sensitive Levels, Sensitive Summary, and Sensitive Details.  Sensitive Levels security applies at the Object level.  Sensitive Summary and Sensitive Details at the Budget Account Number level.

For example, if the Object "5100" was assigned Sensitive" Level 1" and the user was only assigned a level of "Non-Sensitive", they would not be able to view the information for Object "5100" anywhere in the system, including the Payroll module, Reports and Budgets. 

Please note, provided a User has been assigned appropriate Sensitive Level, Sensitive Summary and Sensitive Detail security, if an Object as been setup with "Adjustment" on Manage Objects/Manage Budget Accounts and the user has been assigned "Write" permission on the OrgUnit Permissions tab, they will be able to make changes to Payroll amounts through the Accounts Details tab/Adjustments Sub-tab even if they have not been given access the Payroll Module.

See related articles:

How Does the Sensitive Hierarchy Work (Why Don't I See Data)?

When and Why Do I Use Sensitive Levels and/or Sensitive?