Ok, I'll bite......
Unless the award or employment contract makes provision for this I would think it not legal to withhold wages.
Wages for full time employment should not be delayed, however employment on a casual basis would require the reporting of hours worked in order to calulate entitlements.
That said - labour hire companies, whether employing on a FT, PT or casual basis, commonly pay wages based solely on submitted time sheets - and only then if counter-signed by the client who engaged the labor hire firm.
The example supplied says timesheets are required only on "particular projects" - indicating timesheets are NOT used to calculate wages but only to invoice clients.
How should you and your client handle the situation?
Pay weekly payroll entitlements as per normal.
Employers should clearly communicate and consistently enforce their time-sheet policy so all understand the problems caused by tardiness, and possible consequences for their employment. ie. Enforcement might include verbal then written warning, adverse entry in employment record, spot-check/retraining, disciplinary hearing.
A carrot rather than a stick might be more productive. eg. Employment agreements could state only timesheets submitted on time would be considered when calculating performance bonuses.
Of course if this issue ever becomes relevant for a client in the future I will be sure to refer your authoritative answer in this thread before embarking on any course :-)
Edited at 29 Dec 2013 12:52 PM GMT
Edited at 29 Dec 2013 12:54 PM GMT