Buddy says:  There is no formal definition of a "casual" worker.  However, it is understood to be a worker who supplies their labour or services in irregular or informal working arrangements under which there is no obligation to provide or accept work. 

Further information:  The primary issue with casual workers is whether, notwithstanding the casual basis of their work, they actually constitute employees. If they do constitute an employee then they will have various legal rights, such as the right not to be unfairly dismissed, protection under TUPE, the right to flexible working and the right to be informed and consulted about collective redundancy. 

Whether or not someone is an employee is determinted by reference to a number of factors including mutuality of obligation and the level of control that an employer exerts over the employee's work. 

Mutuality of obligation occurs where:

• The employee agrees to provide personal services; and
• In return, the employer pays a wage or other remuneration.

If the worker does not have to provide the service personally, for example, where s/he has an unrestricted right to substitute someone else, then there can be no employment relationship.

The level of control that an employer exerts over an employee's work is higher than the level of control exerted over a worker.  It is by no means clear what level of control is required for a worker to acquire employment status, but the following are relevant:

• The level of control exercised over employees in the business or in that industry.
• The manner in which the work was performed.
• The place and time for the performance of contractual obligations.

Also relevant in considering employment status are the intentions of the parties, the practice within the industry, how the contract operates in practice, whether the worker took any profit/loss risks, the facilities offered to the worker by the business and the mechanics of any disciplinary/dismissal actions and the mannter of payment.

If the individual in question satifies the mutuality of obligation and control test, and, if the other factors mentioned above are consistent with the contract being a contract of employment (either written down or implied), then the individual is likely to be an employee, casual or otherwise.