The posting of costs and revenues can be locked or restricted via different parameters:
globally
with the Time recording key date planning model parameter in the Model and Model Parameters module. This parameter restricts the period for the recording/posting of actual data for all projects in the system.
per project
with the Locked parameter in the Attributes/parameters area in the Project Core Data module. The recording/posting of actual data is thus not possible on any of the project tasks.
per task
with the Task locked parameter in the Schedule module. Using this parameter you lock the recording/posting of actual data for a particular task.
Customizing details
In the module customizer you can use the Time recording lock parameter to define how the above mentioned parameters behave.