A worker of mine is on a daily rate but only worked half a day, how do they submit a timesheet to reflect this?

Timesheets can be submitted for a portion of a day by following a formula

If the contractor is on a daily rate and only works a portion of a day, they would simply divide the number of hours worked by 8 to obtain a decimal unit to put in your timesheet for that day. You could also refer to this chart for ease