The evidence that you need to supply depends on whether you are meeting the skilled employment requirement or the Australian study requirement.
Overseas or Australian skilled employment:
Certified copies of your work references for any positions held during the relevant period. Your work experience references must meet the following requirements:
the reference should show the official letterhead of the company or government department providing the reference
the letterhead should indicate clearly the full address of the company and any telephone, fax numbers, email and website addresses
the name and position of the person authorised to sign the employment reference should be typed or stamped below that person's signature – a reference with an illegible signature will not be accepted
the direct contact number of the person writing the reference should be included in the letter
the letter should indicate the exact period of employment, including whether permanent or temporary, full or part time, position/s held, the main five duties undertaken, and the salary earned – positions should not be described by generic titles (for example, research officer, public servant) but according to the nature of the duties undertaken (for example, research chemist, accounts clerk)
a payslip from your current employment should also be included – this is especially important for applicants working in government departments.