Requirements
Holders of this visa may be employed for a period of between three months and four years and may bring any eligible family members, including same-sex partners, who have unrestricted work and study rights in Australia. Holders of the Subclass 457 visa have no limit on the number of times they travel in and out of Australia.
Employers must be approved by the Australian government as an eligible employer. Employees are restricted to working for their Sponsor and may not work (or volunteer) for any other organisation. In order to change employers, the employee needs to arrange for their "new employer" to become a 457 Sponsor, if they are not one already, and then lodge a 457 Nomination. Once the nomination is granted the employer obligations will shift to the new employer and the visa applicant is restricted to only working for them. There is no need to apply for a new 457 visa, unless there is less than 12 months remaining on the current visa.
Employees must also meet minimum levels of qualifications and English language skills, in addition to character and health requirements. For these requirements see the 457 visa checklist. Some trades and passport holders from certain countries may be required to do a skills assessment (see the TRA WEBSITE).
Whilst the employer can nominate a person for the particular position they are trying to fill, it is the Department of Immigration and Citizenship which determines whether the criteria for visa grant have been met.
Read more about this topic: 457 Visa