@EAP it was mentioned in the EA MSA Booklet:
Any claimed work experience over 12 months must be
supported by documentary evidence. However, for career
episodes based upon engineering experience, documentary
evidence of employment must be also provided regardless of
the duration of employment.
If the documentary evidence of your work experience is not
in the English language, you will be required to provide a
translation. All translations must be carried out by an
authorised translator (see Item 4 Section A).
Documentary evidence in support of work experience claims
must be on a company letterhead (including name and
location details) and include the date of document, name and
status of author, dates and duration of employment and the
title of position occupied.
You may refer to this for further information:
https://www.engineersaustralia.org.au/sites/default/files/shado/About%20Us/Migration%20Skills%20Assessment/msa_booklet-5august2015.pdf