If you are making "all in" or gross payments, whether it be casual or permanent, you need to specify the award, the classification and the base rate of pay for that classification, so that you can show that overtime, allowances and loadings are included in the gross hourly or annual rate. If you do not, the employee might later claim entitlement to overtime, allowances, and annual leave etc. This risk is heightened for casual employees, as highlighted in Williams v Macmahon Mining where a "casual" employees with seven months' service was found to be entitled to permanent employment benefits, including annual leave loading. Fortunately for the employer, the annual leave entitlement could set off the entitlement to annual leave against the gross pay, because the contract of employment contained a clause as follows:

"The rate of pay is all inclusive and takes into account all responsibilities, disabilities, allowances and other factors associated with the work, location and environmental factors and includes payment for all hours necessary to undertake your rostered duties, and as a casual employee, a loading in lieu of paid entitlements. The rate includes compensation for any necessary shift, public holiday and weekend work."

Williams v Macmahon Mining Services Pty Ltd [2009] FMCA 511 (28 May 2009) 
http://www.austlii.edu.au/au/cases/cth/FMCA/2009/511.html

We understand the ACTU is running mid-year campaign to convert casuals to permanent, and that about 20 out of 120 modern awards require you to give casuals a right to elect to become permanent after 6 months regular employment.