To be AVETMISS compliant from January 2015, all training organisations that submit data to NCVER will need to include the USI. The USI must be collected before awarding a certificate of attainment, or before you report to NCVER, whichever comes first.
You should note that enrolment is not dependent on students having a USI. RTOs may wish to enrol students who do not have a USI at the time if they find this expedient or necessary. Before doing so RTOs should also be mindful of any contractual obligations that their funding body may have stipulated in relation to the USI. More information.