@rp19
Bro I think hindi possible na supervisor mo lang ang gagawa ng COE mo. You can check the ACS COE requirement. You should submit the official COE with the official letterhead.
Kung none existing (sarado na) yung company nyo, you should opt for the statutory declaration (affidavit).
Basically, under oath, i-attest nila na you are working on the same company and you were supervised by him. Para maging valid din ang statement ng manager mo, need nya mag provide ng officialCOE from your employer.
Ang mangyayari kasi, ibabackground check din nila supervisor mo.
Yung character reference ko sa stat dec ko, nabalitaan nya sa HR namin na may nag background check daw sa kanya.
Pero for as long as exisiting pa company nyo, need mo tlga yung official COE with official Letter Head