Use
In certain situations it is useful to post particular cost accounting wage types to fixed cost centers or to orders, instead of to the employee’s master cost center or to another specified cost assignment. This is known as Posting to a Fixed Cost Center or Posting to Fixed Orders or Standard Orders.
Posting to a fixed cost center is usually necessary if directly assigning costs to an employee’s master cost center would be incorrect from the cost accounting point of view. By posting to a fixed cost center or to a standard order, the Controlling (CO) department receives the costs in a summarized form, separate from the amounts assigned directly. Repostings can then be performed within Controlling, according to other criteria, for example, the number of employees or total remuneration.

Prerequisites
You have set up posting to fixed cost centers in Payroll Customizing (under Reporting for Posting Payroll Results to Accounting
® Activities in the AC System ® Set Up Fixed Cost Postings).See also:
Example: Posting Without and With a Fixed Cost Center