I need a bit of advice related to work experience. When I obtained assessment letter from ACS I showed them 4 years of work experience. I provided them with reference letters for all the four years.

Now when I am about to lodge an application, I need to obtain work references addressed to DIAC, for which the requirement is last three years for work experience. So will it be suffice for me to obtain references for last three years and not the entire duration for which I have worked.

Please advice.

Yes you have to provide evidence of the years that you are claiming for, other then experience letter attach tax receipts, bank statements, offer letter from company or any other employment proof.