Both the superannuation guarantee and income taxation legislation rely heavily upon the concept of ordinary time earnings. Statutory superannuation is not payable on non-ordinary time earnings. Employers must withhold PAYG tax from the remuneration of employees, and remit it to the Australian Tax Office.
However the definitions are slightly different and this often causes confusion with employers and employees alike. For instance overtime does attract income tax, and therefore must be withheld by employers, even though it is not generally regarded as ordinary time earnings. However statutory superannuation is not payable on overtime despite both relying upon definitions of ordinary time earnings in the respective legislation.
Here is a useful link to the ATO’s rulings on the definition.