Generally speaking your responsibility to pay SG contributions on behalf of employees ceases when they leave your employment.
However, the last payment may not be due to be paid until after the employee leaves, particularly if your payroll system is such that contributions are paid on a certain day of the month that may be after the date of the employee leaving. In this situation you are still required to make the final SG payment on behalf of the employee.
There will also be situations where you will be paying employment termination payments (ETP) as employees leave your employment. In most cases you will be making a lump sum payment to the employee.
If the employee would prefer you to transfer their ETP to their accumulated super fund you can only accommodate their request until June 30, 2012 and should make sure that the payment fits in under the current transitional arrangements.
For further information about this you should visit the Australian Taxation Office site.