Client Hours represent the hours billed to the client. They take up the same value as Actual Hours by default. Actual Hours represent the hours an employee has actually worked on an activity, which can be the payroll hours too. One way of writing up or down an individual time entry is to split Actual Hours and Client Hours. For example, let's say an employee has worked on a project, but the work doesn't meet expectations. You can enter those hours as Actual Hours, but leave Client Hours blank or enter less hours for it. This way, the employee receives the credit for working, but the client isn't fully billed for the activity.