@archdreamchaser I'm not very familiar with a statutory declaration but afaik it has a format specific to AU. Here sa pinas we call it affidavit.
According to Vetassess, u need a statutory declaration (or notarized affidavit if outside AU) if your reference letter couldn't be in the official letterhead of the company.
See http://www.vetassess.com.au/portals/0/downloads/qualification_assessment/srg1%20explanatory%20notes.pdf?id=31082016214952 (Appendix B and C on the last page)
I had a notarized affidavit done because the COE provided to me was generic. I did not follow a specific format, I just made sure the requirements by Vetassess (found above in Appendix C) were clearly stated. I was also very specific in outlining my roles and responsibilities, even more specific than in my CV. I referenced my r&r if it is the same/very similar to the job description of my nominated occupation as stated by Vetassess.
Anyway since it was just a letter I made and had my previous managers signed, it couldn't be an official company document hence cannot be in the letterhead. I just googled template for affidavits then had my statements notarized.