Billable and non-billable time and expense entries may differ, but it is usually not a best practice to manage those differences during the time and expense entry process. It is often unknown whether or not those entries are billable during the entry by the resource. Editing control of billable versus non-billable settings in the time and expense entries is often disabled for resources for this reason.
It is often most productive to leave billable and non-billable entries as equal, but differentiate during the invoicing process. Reporting the variances between billable and non-billable entries is then done following the invoicing process by reporting the variances between billable and invoiced entries. This way we know the difference between what we would have billed, had we billed on a straight time and materials basis, and what we actually invoiced.
An exception for allowing changes to billable versus non-billable settings during resource entry can be made if resources are accountable for managing their own billable versus non-billable time and expense. An example of this could be a law office in which only the attorneys are entering time and expenses. If they know what is and what is not billable when they add new entries they can save time sorting it out later by including that information now.
Project managers can manipulate time and expense information, including billable and non-billable, if the entries have not yet been approved or invoiced, but usually do not. An exception in which project managers may manipulate time and expense billable information would be in an environment in which the project managers are responsible for determining the final invoice amount for all entries, but do not perform the Project Insight invoicing process. This is very uncommon because any environment in which the project manager is responsible for the final billing is often an environment in which the project manager can also perform the invoicing function and therefore manages the difference in the invoicing process.